Starting with 600?!?!?
Start at 1500, then 2000, then 3000.
I use mag wheel polish to polish back out, works like a CHAMP.
In your case, I'd go over them again with 1500, 2000, and 3000, and make sure you are wetsanding. Keep everything as wet as possible. That will keep the surface cool, and lessen the risk of heat-blistering.
1995 Jeep Grand Cherokee Laredo, 4.0L 2WD, 355,000 miles.