Don't know much about pumice - never used it. People here often talk about using pumice on strops... I have sanded strops though: 1000 - 1500 - 2000 grit wet / dry. You have to make sure all the particles are removed from the leather when you are done.

This sanding thing is NOT recommended unless one is advanced, from what I hear. I did it on a strop that I could ruin and not regret it too much. Turned out fine, works great now.

Having said this - wait for the response for one of the stropmeisters

Cheers
Ivo