No expert here; but what I would try first (I mostly mix heavy-metal type guitar) is cut out anything below 100hz or so on every guitar with a good 48db or more high pass filter. Then watch out for the 500hz regions for mud.
 
Then timing becomes very important, a lot of slightly-out-of-time notes are going to make things messy.
 
To make a bigger sound with fewer guitars, add a pitch decrease or increase in hundredths of a semi-tone to a couple of the guitars.

Below is the**UNLISTED** link to the video, please don't share it...the song is only a day old so it's very rough, and I'll remove the link before too long to avoid additional personal embarrassment. 

 
Your rough mix is better than my mastered tracks. Nice work, Craig, and a very cool song indeed.

kevinwal

Below is the**UNLISTED** link to the video, please don't share it...the song is only a day old so it's very rough, and I'll remove the link before too long to avoid additional personal embarrassment. 

 
Your rough mix is better than my mastered tracks. Nice work, Craig, and a very cool song indeed.

Thanks, but also remember that the fewer tracks you have, the easier it is to make a mix that works. There's a domino effect with "less is more"...everything becomes simpler, including mastering.

This comment below by LLyons really struck me. Often, because I focus on the technical, I forget the importance of emotional impact. So much good information in this thread. Thanks Craig Anderton for posting your song. It clearly illustrates the possibilities of a full sounding mix with few tracks.

LLyons
One thing that helps for me - I try to flesh out the purpose of the song before I start. Not all times, but more often than not. When I'm recording, I ask myself 'does this part support the theme, emotion and lyrics of the song'. If it does, I keep the track. I might not use it, but it's there. I usually delete any track that doesn't fit, before I even get to the mix process.

im beginning to learn, sometimes less is more.
even EQ ing guitars these days, not going crazy like I used to..trying to remove every offending frequency.
now a hi pass / low pass and cut where the harshness is and its done.
 
I am one of those people grew up on an 8 track reel. you used those tracks to their fullest potential.
panning drums on 1 and 2. bass on 3. guitars on 4,5 and 6. then vocals went on 7 and 8.
most of the time recording vocal on 7, live bouncing back ups to 8, then re recording 7 as the lead vocal.
 
I created some great tracks using only 8 tracks.
long story short, I get a DAW and somehow my track tally went up to 30 tracks.
so many years ago I decided to go back to basics. my projects do have a lot of tracks, but those tracks are not always playing simultaneously. the more tracks, the harder it is for separate instruments to stick out in a mix.