This is exactly your problem. Use smaller wheels like GS said to better get at the hollows of the blade and of course to lower your RPM a bit so as not to throw your layer of compound before it sets,it'll also help prevent over heating of your blade. When funds allow you may want to follow through with your idea of the belt driven buffer,use a quarter to half horse low RPM motor and a step pulley to allow full RPM adjustment and if possible buy or make a leather faced wheel. I made mine by plying 6 discs of leather together with gorilla glue and turning them true to center with a file while under power at the lowest RPM setting,it worked perfectly. I hope it helps.