My first/last song was mixed and mastered by a 3rd party... I realized nobody knows/understands your song better than you do (especially when you are paying not so much to do the job), so I have decided to mix (definitely) and master (not so sure yet since I have not watched enough youtube videos on mastering yet , hopefully Ozone 5 will help do the job) my next song. 
 
Question is, if you are doing your own mastering, are you not better off having a mix bus where you can hear how the song should sound like (blending/levelwise) and then let that mix bus go to another bus (master bus) where you try to perform the mastering job (segregation of duties kinda stuff)?. 
 
Mix bus -12db and Master bus 0db (after processing) sound good?
 
Thanks in advance.

I suppose you could use an additional buss to the Master buss, but since Ozone (and most plugin's) have a bypass function I don't really see any point to it. If you want check the mix simply disable Ozone, or any other plugin's you have on the Master buss.
 
Dan

I run separate mix & master busses.
 
It costs zero overhead and increases your flexibility.
 
I often run separate exports of mastered/unmastered mixes to 2 sets of stereo outs on my interface

I honestly believe that mixing and mastering cannot be done at the same time. Personally I feel it is a big mistake. After a long mixing session there is no way you can make rational decisions about mastering processes. It is actually pointless to do so. (Especially if you are mastering your own work)
 
Do your great mix and then burn that to a CD and wait a week. Listen to your mix quietly here and there. In the car, on other systems etc. You will start to pick up little things about the mix that are not perfect. Something a little loud here and there, entrances and exits, too much clutter going on in one spot etc...
 
Then setup a totally new and fresh mastering session. (No extra buses required) You will always get a much better master doing it this way. You ears will be fresh and it is like hearing it all again for the first time. (Something a third party mastering engineer gets to experience)
 
What is the hurry? If you want to do something really well, it will take time. Some people say around here you can do it at the same time but if they used this approach they would always master better. Simple as that.
 
Even back in the old days when famous mix engineers were forced to master straight after a mix session in order to get the record out to satisfy the record company they most often said later thay regretted doing it that way and they would have mastered it differently. I have read that so many times in interviews with some very well known people. Listen to what they are saying, not just me!
 
To the OP I know this does not help you and I apologise for that, I am simply trying to make you rethink your strategy. Often that removes the need to solve a technical issue eg setting up multiple buses at the time of mixing.
 
I can almost guarantee that if you wait a week to master you will:
 
1  Use far less EQ on the overall mix because your ears are not tired and you can really hear what the EQ is actually like
 
2  Use less compression and you won't be slamming it anywher near as hard. Slower attack, gentle compression only.
 
3 You won't be pushing your limiter as hard because your ears are also not tired and you will find you can get the limiter pushing overall levels up without working too hard at all and you won't hear the limiter either. (changing our sound that is)

I would listen to Jeff. Everything he is saying I fully agree with. 
 
To me mixing is the harder process. If its done well mastering should be fairly easy. 
 
One thing is never be afraid to go back and remix if it seems it just wont sound right when you master it. 
 
Start with great mix and it will master itself. 

I don't mix for radio or mass distribution or anything. I just mix for my friends.
 
My mixes never get so finished that a subtle eq or additional compression will matter.
 
I'm lucky if anyone listens. :P
 
So I do it in one, with one master bus. I do use an EBU meter (RME's DigiCheck) which measures average loudness. I try for a tiny bit of limiting (a couple of dB at most) with an average loudness around -14 and set the compression accordingly so the music fits there.
 
I move the faders up and down to make it sound nice. :-)
 
I usually have so much to mix, I'm really limited by time. I make a couple of several hour recordings a month and that keeps me busy mixing all the time (I have a day job). I'm usually forced to move on from a mix because of the new recording waiting attention.

I bounce my entire mix to a new track in the project and do my "pseudomastering" there. This way a given song is all in one place. It's an extra step, but it helps me delineate between mix or master. I will sometimes let it sit for a day or so, but I'm pretty impatient to put off the final touches much longer. And by "pseudomastering" I mean doing final EQ tweaks, some gentle multiband compression if needed, using Ozone to get the bass frequencies mono and a limiter that is hopefully transparent.

A lot of what I have said also applies to more professional gigs where one may be doing a mix and mastering job for a band etc and getting well paid to do it.
 
Of course there is nothing wrong with doing some light mastering on a track you may be working on for fun. But the wait a week thing still is good even for the mix only. After doing a mix I almost always find one or two things that just need changing up and it is usually worth it. These little niggles just seem to slip through the cracks and go unnoticed. If you master straight after a mix you have locked that mix in a way.

I am new to this as well.
 
From what I gather here, I would finish the mix and then bounce it to a stereo track, then export it to a new project where I would then master it?
 
TNX

As others have said, mixing and mastering are two separate processes.  If you are mastering your own mix, it is best to separate the processes however you want to.  Jeff's idea of waiting a week or so is good.  If you don't have a deadline for your own stuff, burn a cd and test it over the week in the car, living room, wherever to get an idea how it translates.
 
Typically, going from -6 dB to -.01 via comp/limiting will bring some elements out front and mask other sounds.  Until you can "hear the future" the more time you spend tweaking a mix based upon a master the better.  It is something else to learn.
 
@