From everything I have read, a belt works just fine as long as it has no metal bits on it obviously. A wider belt would be better - maybe a couple inches. But as long as it's reasonably clean and in good shape, there should be no problem with it.

A couple people here have been using a belt for quite a while, and say it works fine, so I imagine it's not a *lot* worse than a purposeful strop.

I don't think tanning is necessary. As far as which side, think of its purpose. "If I were a razor-sharp blade with microscopic bits of misaligned metal I wanted straightened, which side would I use?"