When you apply compression you need to think of a few things, am i applying this for gain reduction and control, or am i applying this for sound design purposes? For instance, on a snare drum most of us strap one on the insert to get more crack and squeeze more tone out of the drum. A slightly slower attack time like 16-30ms will allow the initial smack of the stick to come through uncompressed while the release of maybe 100-150ms will bring up the full tone of the drum and it lends itself a bit better to eq in my opinion, when you compress correctly.
So my point is, when you turn on the compressor, what is your goal? Do you know exactly what oyu need to do with it? Or are you just turning it on because you think it may need to be there but dont have a clue what its gonna do when you flip the switch.