Guns and Dremel tools do not make a very good combination for the occasional user and can be very destructive.I have restored quite a few "beaters", but it is a gradual process and takes some effort,time and a little know how to have good results.Using home power tools is not usually the ideal way to go.The best advice that I can give is to take your time, start off with mild abrasive polishes that are applied by hand,stay with the contours of the gun and avoid rounding off the the sharper edges.Work one area at a time instead of trying to do it all at once.Most of all enjoy your hobby.If you really want to have that perfect finish,whether the choice is polished,brushed,matte, or bead blasted then maybe the best option is to have someone with experience do it properly for you.