If you haven't already heard there is a free plugin available from FXpansion called DCAM FreeComp. It's an SSL type buss compressor. It sounds great and is amazing for the poor producers out there or anyone for that matter.
Go here FXpansion - DCAM FreeComp
and sign up for the free download.
I also have matched the presets from the Waves SSL Compressor and saved them for use with DCAM FreeComp inside of ProTools. I didn't match it based on sound. I only matched by value but please remember that the Waves SSL Compressor has release and Rate-S settings that the FreeComp does not have so the match may not be perfect but I did include the signature presets also.
Here is the presets. DCAM Free Comp Waves SSL Presets PT10.zip
If this is helpful I will upload for other D.A.W.'s also such as VST and AU presets.