You can get much of these things at Sears, Home Depot or Lowes. Eastwood Company has the cutting bits for a pretty good deal if you can't find them local.
1. Non-ferrus cutting bit(s)
2. Sanding drums in course grits
3. Flap wheels in medium to fine grits
4. Crossbuffs
When cutting with the cutting bits, cut to 90-95% of your total new port shape. Once you have the shape you want, all the imperfections semi-cleaned up and any other misc. crap (valve seat to head mating area smooted out, under valve area, etc) a
You left some room for minor errors and to be able to use the sanding drums to get the final desired shape and smoothness without going too big. With the flap wheels and crossbuffs, all you're doing is removing the courser grit scratches.
With a project like this, it can make things go a lot faster and better to have a set game plan. Once you've accomplished the desired results with each bit, move on to the next. Just don't rush yourself, or you may have to step back to the previous bit to redo something.