When using decapitator I try not to go over 2.5 on the Drive, above that It's just too much and cheap sounding. Don't get me wrong since I find it really good, but saturation is this thing you have to go little by little and adding tracks. I really dig the A, N and E. The T and P they just don't sound good to me.
I have worked on analog consoles and tape machines for decades and saturation is just there, but you don't realize it, is like the air you breath, you just have it and don't think about it, but if you over do it you get dizzy.
For me (saturation) it has to be a global color you give to the song or whatever piece of audio you're working with. Mind operational levels even working ITB and choose a nominal level and treat it so across the board. Of course there are some tracks you really need to push but just be careful.
When working with the filters on the decapitator jut be really aware of not introducing resonance on the corners, you gotta have a reliable monitoring and a powerful reason for doing so since it is easy to have un ugly bump be it on the lows or highs which some time are easy to get used to them when working long hours, your brain just accept it.
Apart from having your main monitors, is also good to have some boombox or alike stuff for checking things. I like to check on this cheap stuff since they sound so bad they give you a great opportunity for checking areas that sound kind of ok on the mains but they may sound bad on these kind of speakers. I also like to check stuff by bouncing and exporting to iTunes and then check on different headphones, good ones and bad ones. You'd be surprise the sort of things you find this way... just be careful with the filters, I am not saying to stay away from them.
Anyway ... just to finish... Place a saturation plugin on the Master fader also, and play around, but be careful with the level going to the bus, try to trim the whole mix if your levels grow too much since it will drive or saturate even more. I used to place a decapitator on the 2bus but nowadays I place a VCC and UBK-1, lately I like the Omega458a, @-20 as reference and then some parallel with a Hardware Vulture. This way it just sounds more real IMHO.
And again MIND THE LEVELS, do the saturation with processing instead.