[dsraven]

if you are using an actual grinding disc you may want to try a flap disc, just for giggles. it will surprise you. they also don't generate as much heat when using them as long as you are aware, like using a grinding disc and knowing that too much heat generated will produce more body work from warpage. they come in different grits so the finish can be done with a higher grit and be fairly smooth, actually.
I have several el cheapo deluxe mini grinders and they all have a different type of attachment. some are 4", a couple are 5". one has a wire wheel, one a cupped knotted wire wheel, one a flap disc with 40 grit, another 60, another 80 grit another an actual grinding disc, several with zip discs of different states of wear (sometimes you just need a small wheel to fit into a tight spot) and lastly a large and small shrinking disc. after that I also have several 1/4" die grinders with burrs of different shapes. the grinder with the extended shaft also is a handy one sometimes. harbor freight sells the stuff pretty cheap (especially compared to Canadian prices)