Go to car shows and swap meets and buy die grinder bits for 5 a piece. I live near a lot of aerospace so I always see new carbide bits and sandpaper rolls for sale. Some minor flaws, most perfect. I wouldn't waste time with stones.
I got some carbide burs... went to Mcfaddendales, an industrial hardware store here in town... they were like 55 bucks for 3! Amazon is cheaper...the stones are just to smooth it up after if I feel like I need to.