Beginner question

Start by selecting every track you want to add a send to.

Right-click in the gray area to the left of the FX bin to invoke the context menu. Select Insert Send -> Insert Send Assistant.

Choose "send to existing bus" or "new bus", depending on whether or not you've already created the effects bus.

You can insert an effect via the insert-send assistant, or just add it to the bus the normal way. Do not check the "Pre-Fader" option.

On the bus, make sure the effect is set to 100% wet if the effect has such a setting. Reverbs always do.

Nothing wrong w/ compressors or eqs on individual tracks.  That is usually the way it is done.  Buses are for reverb, usually, or to combine different instruments.  Say a "drum" bus or "guitar" bus.  Those can share the same fx, of course, but also an EQ and/or compressor.

I'm not familiar w/ MC4, but that is a way to do it, too.  Just be sure to route the sub buses to the master, or you'll wonder where your sounds went ;-)

Hope the above helps - it is confusing when you get started. 

@

Actually, when I do the INSERT new stereo bus, it automatically points the new bus output to the master.... the only thing I need to do is point the tracks I want in the bus to the bus.

You can put the plugs in the tracks if you have enough computing power. If you have an older computer or are using some CPU intensive plugs, popping them in a bus saves the valuable CPU's.

These are all very fine responses. Reading them from a newbie's perspective might be frustrating, so I will give you the skinny with explanations:
 
First, two different methods for applying an effect to multiple tracks are mentioned here. Both methods use a bus as the location for the effect. The difference is that Bitflipper talked about an 'effects bus' configuration and Guitarhacker talked about a 'summation bus'.
 
An 'effects bus' configuration splits the signal and routes (formally called an 'auxillary send') one of the splits to the bus where you have the effect in the fx bin. The aux send is affected by its gain control and optionally the fader control for the track. After processing, the output of the effects bus goes on to the master bus (and to your main outs or whatever). Many tracks can feed into the same aux bus. Each track will have its own gain control on the 'send'.
 
With an effects bus configuration, you are creating a parallel signal that is processed separately and then recombined with the original in the master bus.
 
The 'summation bus' configuration combines the output of all of the tracks that you want and routes the signal to the bus that has the effect, and then the output of that bus is routed to the master bus. You're basically inserting a new bus into the path from source track to master bus, but only for the tracks that you select. 
With a summation bus, there is only one signal that is routed through the sum bus before going to the master.
The 'effects bus' configuration is more flexible than the 'summation bus', allowing you to do more with the signal before it goes into the effect and more to the signal after it is processed, but it also has more moving parts. The summation bus is simpler to set up and operate.
 
The sum bus is well suited for things like combining all of the individual drum tracks into a single stereo bus that represents the complete kit. Or grouping all of the guitar tracks together and separately all of the vocal tracks together in order to balance one against the other using only two faders.
 
Even though a sum bus is not the absolute best for applying the same effect across multiple tracks, I still recommend starting with the summation bus technique until you feel comfortable with it and then try the effects bus technique.

bitflipper

I can't believe I've been on Sonar for almost 5 years and never knew how to do this!!!

Dave, it was a new feature in 8.0, so it's only eluded you for 2 years, not 5.

Previous versions had a module that had an aux 1 and 2 send and return panel, and each track had it's own selectable pre/post level. Basically the same thing as was explained by Kicker and as you would find on a basic mixer.
 
Obviously the OP has not been through the tutorials or looked at the demo tracks to see how their mix is set up!
 

Guitarhacker


I have MC4 which doesn't have FX sends... but I can do this by adding a NEW Stereo Bus and then inserting the FX (reverb etc) into that bus's FX bin, and then simply directing ALL the tracks (outputs)  I want to be processed to that particular bus.

 
 
 
Herb - I'm using MC4, and use FX sends (usually to reverb bus) on the tracks. I just expand the track in the track view, right click in the grey area and choose from the menu. (it's been a while mind you, ain't had time since the baby's been on the scene!)
 
Cheers