i have stripped quite a few coated blades and some coatings are hard to sand off and require a stripper or belt sander to remove, others sand off fairly easy. most coated blades are coated to hide dimples or imperfections in the grind that are left over from the grinding process. if you want a nice satin finish and there are dimples or deep sanding lines you have to remove them first.
its best to start with a 280 grit sandpaper and work up to at least a 400 grit but you can go a little finer but if you use a stripper and the finish under the coating is not bad, you can start with 320 grit. 3m wetordry sandpaper is a good brand to get.