the papaya tabs are crammed full of extra papaya and pineapple enzymes, which are supposed to be good for breaking up ingested fur. the only downside is that they do contain some sugar, so if you're giving a daily ration of fruit (1 tsp per 2 lbs body weight is allowed per day), I would cut back on the fruit on days where you give a papaya tablet.
as far as other supplements go, I don't know of anything that's really necessary/helpful unless your bunny has chronic health issues (joint problems, digestive issues, etc.)
the best way to deal with the poops, though, is to up her hay intake if you can and groom her as much as you can get away with. I love my furminator - I got the longhair furminator for cats under 10 lbs and it works wonders on my lionhead and holland lop in just a few minutes. it's WAY better than a brush (which I find pretty ineffective). the furminator comes with a money-back satisfaction guarantee, so there's nothing to lose by giving it a try.