what is the best way to remove powdered sugar off of fondant?

I just brush it off with a paintbrush or you could try a damp ( not wet ) brush to get it off

You can use a paintbrush dampened with something with alcohol. I used clear vanilla and some people use vodka. It will evaporate leaving the fondant clean.

Ditto to the above advice. I use a dry brush first and if it needs more help I use a damp (not wet) brush.

ok great, thanks guys!