When I cut, I find the most effective way is just to use the crop tool, get out most of the rubbish you dont want there, then get the lasso tool, go around the shape of the thing (try and leave about a half a CM of background around the player of whatever it is you're cutting) then zoom right in to 1600%, and using the eraser (I use it on 3px) just go around the outline of the player, you'll get a close cut to the pixels this way.
It sounds time consuming, but it isnt really, the cuts I did on Franchise4Evers "24/7" sig (which seemed to get high praise from a few people for the cutting being so crispe) took around half an hour to cut both.
Also to make it easier for you, if you're cutting somthing for a sig, down size it to fit the signature first, that way you save alot of time, as the bigger the photo, the more time it takes to cut.
As for the Brush thing, I dont know what the deal is there, maybe because its only the trial version?
I dont understand your filter question, what do you mean by adding colour once you've done a filter effect? (I rarely use Filters BTW)