I have had a Baja No Pinch tool, ever since I was turned onto them by someone on, maybe, Thumpertalk and it, along with a valve stem fishing tool, have been a couple of the best tools I have ever bought as it was always a nightmare/excercise in frustration in dealing with getting the valve stem through the rim hole.
Ever since getting the Baja No Pinch tire tool, I have not damaged one single tube and I have changed at least a dozen, if not more, tires on both my 21/18" rims, but also on the kids TT-R 90 and 110 with the smaller axle rods. Pushing the beads up and over the rims is a joy as compared to using the tire irons/tube pinchers I used to use.