Some good suggestions by Beat! :-) Just to offer a sligthly different point of view:
There's nothing wrong with bus compression on a MIR Pro-mix (full band and/or multi-band), and there's nothing wrong with stereo-enhancers*) either - provided that you know why and how to use them.
That said, it's the best idea to start with those effects in a master chain you need, and - even more importantly - you know with uncanny sureness. :-) Leave away everything you've just been told on the 'net that "everybody usese this", and/or which doesn't show any desirable effect.
Personally I would start with nothing than a transparent, high-quality full-range limiter with its output ceiling set to about -0.3 dB. Then raise the input volume (most of the time by lowering the threshold level) until the limiter starts to kick in on the loudest hits, but not during longer sustained notes.
For sculpturing the sound, don't aim for any "coloring" plug-ins as long as you really know why you would want to hear them. Use a clean, high-quality parametric EQ instead (Viennna Suite's Mastering EQ is a great choice). A high-pass around 20 Hz is always a good idea, above that you will start to kill important fundamental frequencies. Its a better idea to use MIR's Character Presets for individual tracks, as they will always take care for LF-rumble (if any).
For "glue", a full-range compressor with settings similar to the ones suggested by Beat can make lots of sense. Personally I tend to "mix through" a compressor, which means that it's part of the master bus from the very beginning, so I hear its effect and consequently work with its impact on my mix. But this is no "fire and forget"-solution: I constantly re-visit the bus compressor for minor adaptions throughout the whole mixing process.
Re - Volume: I know that it can get confusing with so many possibilities of changing it. Assuming you're starting with MIR Pro's Natural Volume I would leave every other means of actual _volume_ control alone ("volume" in its technical meaning); the obvious main exception being the master bus volume. Controling your musical dynamics (opposed to the aforementioned "volume") should be done mostly by means of a MIDI-CC of your choice.
*) Regarding stereo-enhancers: Not enough people know about the "Shuffler"-mode of Waves' trusty old S-1Stereo Imager. Originally introduced by the late Michael Gerzon (one of the god-fathers of digital audio), this nifty little algorithm adds some interesting perceptional gimmicks to any signal that's derived from coincident microphones. MIR's impulse responses are captured by means of 4-capsule Ambisonics microphones, which are coincident by definition. The Gerzon Shuffler (used with care!) is able to make a MIR-based mix even more "enveloping" and appealing.
PS: Get rid of the UV-22 Dither. It's a very special "colour" of dither which is aggressivly noise-shaped. Only few mastering engineers would suggest its use for delicate orchestral music. Use something less abrasive as long as you don't see the absolute need for it. - In case you're using MIR Pro's RoomTone, you could actually do perfectly without any additional noise. ;-)
Hope that helped,
/Dietz - Vienna Symphonic Library