Sanding mops are about the best thing since the invention of slice bread.
It's great strength to the scrollsaw artist (IMHO) is softening the hard inside edges of fretwork.
I use a 4" mop - 220 grit - at the slowest speed on my drill press which I think is about 700 something RPM. I know others will use much higher speeds but this is what has worked for me.
One caution to avoid damaging fretwork is to make multiple, light, slow passes in all 4 directions - at the same time firmly supporting the piece using both hands - making sure you also support, with your fingers, the back side of the point being sanded.
If I am working on a large flat piece that doesn't lend itself to the mop being mounted on a drill press then I clamp the piece on my bench and use an old Makita 7.2 cordless drill my wife bought me well over 30 years ago - still going strong and the RPM's are about perfect for my liking. Same routine - multiple, light, slow passes on all 4 directions.
Jay