First and foremost, the clear castings should be post cured well with heat. Otherwise the resin may be to soft to get satisfactory results. Unless there is parting lines or a matte finish, you do not have to wet sand. If sanding is required, start with as coarse as 320 grit (ALWAYS wet sanding) to speed up the finishing process, and gradually work up to 2000 grit for the best results. Progression should go something like this 320-600-800-1200-2000 again, remember, ALWAYS wet sanding. It is reccomended you polish by hand, but it can be performed using a power buffing set-up if it goes REALLY SLOW! To successfully polish you must not go no more than 300 RPMS at the wheel. Use a loose cotton buff and plenty of 3M Automotive Rubbing Compound. It's messy... but it works like a charm! Remember to wear you use safety glasses and use a good respirator or do it outside because it is a mess!!!