Mixing orchestral sounds

[FeatheredSerpent]

I'm working on an arrangement that has cello (using entire register), viola, trombone. There is also piano, acoustic and synth bass, vocal samples, rhodes, and of course drums.

The cello is the main rhythmic foundation with lots of support from the violas, although the violas also play leading parts.
Just wondering if there is any standard techniques for having the strings present and powerful but at the same time leaving enough room for the rest of the instrumentation.

I've created seperate mono tracks for cello (lower register), cello (higher) and violas, using panning to create space, but I'm not an experienced mixer and it's a bit hit and miss on the eqing as I know I need to do some serious cutting.
Also any reverb choices I should be looking at more than others? I've experimented a bit but looking for some solid advice, if indeed there is any particular thing I should be looking at.
Also with the trombone, it seems it is predisposed to start sounding really artificial with even the lightest of touches.

With reverb, slightly off topic from the strings, I'm wondering whether people dedicate a reverb type solely to drums, with other instruments feeding a second common reverb type, with maybe a third for giving certain elements special attention?
Should I look to use techniques like having the left hand strings' reverb panned right and vice-versa etc, to keep presence without overpowering particular parts of the stereo spread?

I know my ears should be the best judge (and they're getting there!), but just looking for some general advice.

Thanks