Sanding off tyres normally done dry. Instead of sandpaper which creates lines that further increase the wear rate, use the 3M scrubbers aka Scotch Brite.
They comes in grades. The best that work with sanders are the abbrasive type and the non abrasive ones. Use abb type to breakin new tyres or removing large amount of thickness. The non ones, use it for cleaning. It will get warm as a result of friction
See and feel the difference before and after; it just simply extra instant grip because of fresh rubber surface created. Do this before any traction compound application.
Just my experience, give it a try, good luck.
Can't say anything about foams tho .