I have a patterned rhythm (a loop) and its components are a bass drum, a snare drum, and two different hi-hats. I would like to mix them, but I can't really separate them. It would have to be a grouped mix. What would you recommend me for doing this (how to EQ, how to compress, what I should try to achieve sonicly) and what would be a disadvantage of taking this approach?
If they're simply on a stereo pair, experiment with traditional wide-band compressors, multi-band compressors & transient shapers, as well as EQ.
Bear in mind some comps can also be used as expanders, so you can 'push' with one & 'pull' with another to get the results you want.
You could also, if it's live mic'd, play with the phase between sources, to [de]emphasise some aspects. Waves InPhase is the only plugin I've ever used for that, though I assume there will be others.
There's no hard & fast rule, you just have to play with things til it sounds better.