The most fascinating thing I ever heard/read about for damping was this thing that I believe was like a flexible, layered duct tape arm--thick enough to have some stiffness--but still flexible. At one end I think you put some folded up paper towels with quarters taped inside them, then attach the other end to the side of the tom somehow. The idea is that the paper towel end sits lightly on the edge of the tom head and damps all the sympathetic ringing when the toms aren't being played (I would call it the "wuh wuh wuh" toms drone). I guess when you get the gizmo adjusted right, the force of the tom hit bounces the paper towel damper off the head and the stiffness of the layered duct tape arm keeps it from flopping back down for 2, 3 or 4 seconds before it settles back down and again damps the sympathetic tom drone. I'd love to hear a more detailed (or correct) construction and application description if anybody knows it.
i can't find it, but a video exists of engineer joel hamilton's home-brew version of this....which if i remember right was just a paper towel with change in it, folded over and taped to the rim. i can't imagine that staying airborne for more than even a second, but it seemed like it worked.
regarding tom drone, i've done takes of the same song with and without toms on the kit, and cutting from the former to the latter really does sound like you just muted a drone track. it's pretty dramatic. that said, it didn't really seem to make much difference once all the guitars were piled on.