There are two tricks to painting wheels...

1. Have the tires removed from the rims and have the area you don't see painted as well as the areas you do see.

2. Find a tire shop that has a rim machine that reaches around the tire and does not touch the outer area of the rim. These machines are much more common today and will not damage the paint. Better yet have someone mount them by hand. I did this once myself (new tires, fresh painted wheels) and can do a tire in less then 4 minutes.

These are both good thoughts, to anyone interested in some particulars, I've painted 4-5 sets and here are some tips.

Blast them totally clean as with anything, bare metal, metal etch, metal treatment converter. PPG DP40/90 etc. as usual. In fact, if you are doing black ones, multiple coats of DP90 (I think that is the black) are pretty much enough if you want a flat black like late bay/vanagon steels.

Major tip: you can never get all the blasting residue out of the crack of the rim to center joint, plus it is VERY hard to get that well painted. I've done 2 things separately and I do now in combination. Brush paint that joint all the way round by hand first off. Then do one spray coat of primer, then use a good automotive seam sealer calk in the joint all the way round. That is what really gets them sealed up never to rust at the joint, and covers residual sand bits. Continue with another primer (or 2 more if using it as topcoat) and then maybe 2 shots of topcoat.

Another good tip: cheapy lazy susan and spin the wheel as opposed to trying to walk round it and maintain a good spray. I put an old 1 gallon paint thinner can on the turntable and set the wheel on it, in fact I just move them around on the thinner cans (I have several.) Typically I use the gun adjusted to about 2" wide spray and do multiple angles working center out and the outside edges, let them dry overnight then do the backs.

As Donald mentions the outside edges are critical for nice air sealing, and tire shop idiots can scratch them up even with better machines. Insist on a machine they do alloys on if you don't want them scratched, but frankly most all places use those now days anyway, operator error can still maul a rim (real important on say a $500 alloy).

I mount/dismount my narrow 5's by hand on an old manual machine I picked up for $25 at a sale. These are pretty common, and depending on the design can be very safe for rims if they feature lead lined parts to run on the rims. I've noted Harbor Freight sells one for about $50, but have no idea the quality. They look like the thing the guy is using in the Bentley T2 manual. You sort of have to watch buying at a sale though as some of the early ones have a lot of parts to mount dismount, can be pretty hard to plain figure out how to use, and be useless if stuff is missing.