I use mainly newspaper in tubs (aspen for some.) Do you completely bleach out the tubs after a BM and use new newspaper? I do, and I never notice any odors.
I would be leary of using anything else. I know that people use something called nolvasan and that is supposed to be good too. But bleach is cheap, readily available and works great for me, so there is no contest. You do have to rinse it out super-well, but I do that.
I use the scrubbie sponges to clean the tubs out.. I go through a lot of them, as the bleach eats away at them :)