DC,
Wetsanding keeps your sanding pad from getting caked with material. I've found the easiest way to wetsand is to let your hose flow lightly on the object being sanded, although you could easily accomplish wetsanding by keeping a bucket of water with a little Dawn mixed in next to you, dunking the sanding pad in it frequently.
The process is simple but you MUST be careful for a few reasons. First, if you're spot-fixing, MAKE SURE you have a perfect match paint OR you are repainting all of the rims. Nothing looks as bad as 3 silver rims and one grey rim.
If you're going to tackle the whole shabang, I recommend removing each wheel from the Explorer. Wetsand each rim till the corrosion is gone. In addition, scuff the finish of the 'good' areas to help in paint adhesion. You can use a very fine sanding paper for this (2000 grit, etc) or a steel wool pad. Either way it'll accomplish the goal.
Once the rim is clean of corrosion and sufficiently scuffed, mask the tire with masking tape and newspaper. Take your time here so you have a nice clean masking job. With the rim completely dry, spray even coats on the surfaces to be painted. Thinner, lighter coats multiple times are much better than one thick pass. The results from many light coats are phenomenal. Allow about 30-45 minutes between coats, unless it's sufficiently warm where you're doing this. If so, 20-30 should be fine.
Once you have a nice and even covering of the rims, let them dry for an hour at most. Then do the same with your clearcoat enamel - light coats from multiple passes. When this is through, let the rims dry at least for 24 hours. Much like autobody paint, it can take a month for a full, 100% cure; however, within 24 hours, the rims SHOULD be dry enough to remount and use.
A few caveats:
(1) This process is not meant if you're unsure of yourself with painting and the like - it's very easy to make a hell of a mess of your rims. Patience, being meticulous, and being careful are your goals. Rushing through it will show in the final product.
(2) If you can get your hands on an air compressor with paint gun, the results would be even better than a spray can. A spray can may be able to mimic the spraying action of a compressed paint gun, but the fine-ness of the paint through a paint gun is much better. It all depends on what you're looking for a final product - perfect or 'good enough.'
(3) This process is EVEN easier if your tires are dismounted from the rim. This way you can sand and repair any 'curb rash' on the lips of the rims. Also, it ensures your lips are the same color as the faces of the rims. Again, this is something that would require significant work, though, as well as cost in remounting, balancing, etc.
Post away if you have any other questions. I redid my FX4 rims when the quality wasn't quite what the seller said it would be. However, they look like they came straight from Ford now. It's all about the right techniques coupled with patience, meticulousness, and care...
EDIT!!!!!! -- Also, if your rims are aluminum faced with a clearcoat protectant, you should be able to get away with removing the corrosion and re-clearcoating. DO NOT SAND THE ALUMINUM IF YOU DONT HAVE TO! You'll make a mess of the natural machining lines...
