So...started out my sanding on the trunk lid using these on my 4 1/2" angle grinder:
1) my angle grinder is 4.5A and is struggling a little - I'll probably go get a 7A Makita or Milwaukee
2) the paint is really thick and it's taking a lot of passes to get down to the metal which wears those discs out pretty quick. There are more rigid discs available, but I don't want to wear the metal down.
When I do get down to the metal, it's got lots of swirls on it. Feels smooth though. I'll try to get pics, but before I touch any other body parts, I'd like to find out if this is a good surface to work with for prime/paint.