When necessary I use Nair for Men on my back. I also have used just plain Nair, seems like both work well--instructions are a bit different--so must be a slightly different formula. Now my store has just Nair for Men. I would shave anything I could reach with a razor--but I like my hair up front--just trim the pubes, I do shave the balls. The back is hard to shave by myself, so Nair it.
Oh and why do I shave the back? It is very hairy and I like to have my partner do fire play on it, also it shows the marks from flogging better when shaved!