Cartridge rolls(grit rolls, "tootsie" rolls) in 40-60-80 or 120 grit on a die grinder.I use 40 grit and 60 grit for aluminum, finer grits just plug up too easily and fast. You will need to get the mandrel for holding the cartridge rolls. Got to be careful not to hit the valve seats or slip and go "scribbling" across the deck surface or intake face. Watch out to make sure you don't hit the seat with the roll or with the grinder collet when you reach in deeper.
Get ahold of you local engine shop and see if they will sell you 2 old valves, an intake and an exhaust, and also grind them down so that they have no margin left. They may look at you funny until you explain why you want them LOL. You use these to drop-in and protect the valve seats while you are polishing the chambers, the current valves in the head will sit too high and you don't want to mess them up anyway.
In the ports, all you want to do is blend the casting and cutter lines smooth, anything more than that requires carbide cutters and a good deal of porting knowledge to not mess up the flow of a good head.
I've found the best deals on small amounts of cartridge rolls at www.competitionproducts.com
. I would recommend you get 30 pcs 40 grit, 10-15 60 or 80 grit as they polish finer as they wear down, or just get the starter kit they offer as it has a little of everything and the mandrels. This is a good stop for engine related parts and tools.
This should be enough to get you started. I would highly recommend
that you get a copy of David Vizard's
book "How to Build Max Performance Small Block Chevy's on a Budget"
, worth its weight in gold to a beginner, lots of pic's and good explanations.