Did the very same thing for my banshee about a month ago. Took a LOT of time and more than one temper tantrum. heheh
I outfitted myself with a couple sisal wheels, a couple tight spiral wheels, a loose cotton wheel, a couple mushroom buffs, several different sizes of felt bobs and a decent flex shaft for my drill.
I took the engine completely apart before I ever started, then washed all the grease and dirt off the case with carburetor cleaner and then blew it dry with compressed air.
Various holes were stuffed with newspaper to try and keep polishing "funk" out of 'em. As the case was pretty smooth to start with, I only sanded those few areas that had scratches or blemishes with 400 grit wet/dry then went to town with the sisal wheel and black compound. I did all the areas I could reach with the wheel, then switched to felt bobs to get into the hard to reach areas. I had to use my dremel with a little tiny spiral wheel for a couple areas too.
Once the entire case was shiny and scratch free, I wiped it down with laquer thinner and a *SOFT* rag to remove all the black compound remnants. I then used the spiral wheels and brown compound. Again, I did all I could with the wheel then switched to various bobs to get into the nooks and crannies.
Once I was satisfied with the shine, I cleaned it with laquer thinner again then fired off the loose cotton wheel with white compound and went over the entire case. One more cleaning with laquer thinner and then I unplugged all the holes and washed it down with dishwashing soap and lots of hot water. I blew it dry with compressed air then gave it a couple coats of carnauba wax. Check out the pics at www.net-cetera.com/banshee
One thing you want to avoid. DO NOT polish any gasket mating surfaces!!! You could remove enough material to cause a leak. Also, be aware of the mandrel itself. You don't want to try working the wheel into an area and scratch the carp out of another area with the mandrel 'cuz you weren't paying attention (Been there, done that!)
Read the online "How to Buff" manual for info on technique - this helped me tremendously.
Some of the other parts I did required a lot of grinding and hand sanding before they were ready to polish. The clutch cover I did was a pain in the butt as the casting was of pretty poor quality and I had to bead blast the old paint off before I even started. It came out ok, but took a lot of work to get to that point.
The suspension link was pretty easy since I could get to all of it with various sanding drums to get it smoothed out before I satrted polishing.
The brake caliper was disassembled, bead blasted, washed clean then required a bit of time with greaseless compounds to get it smooth. Again, a poor quality casting, but came out pretty nice with a little effort.
This weekend I tackle the carburetors.. Not looking forward to those at all...
I'm no expert, but with this forum's help and Caswell's products, I'm having good results.