Treatment used on OHS & AMB(dfhs)

Overheads I always highpass up to 500hz or 600hz and maybe boost a little air on it. Ambiance tracks I usually roll off above 16khz and below 80hz and compress the bananas out of it.
 
Yeah, the ambience is a great track to really slam with compression, then mix to taste. I personally use a bombfactory comp on it, with just a standard eq rolling off some of the lower frequencies. For over heads I use SSL with a bit of compression and a lot more eq. At least use an EQ for the overheads, depending on the style of music cymbals can sound really "drum machine" if they're not sitting properly.