I decided that I didn't like the look of the OEM SS chrome looking fender flares on my dark blue 2000 crew cab. Looked a little "shiney" for my tastes.
So I removed all four mud flaps and then the little SS screws easily backed out to allow the flares to pop off. Those dang flares were packed with silt and when I swept the grime off the fenders I found plenty of rust bubbles.
The bubbles were more prevalent on the lower parts of the fenders which is good because there is good access to both sides of the sheet metal on the bottom half of the fender openings. The bubbles almost all seem to have started at a screw hole and crept under the paint from there.
So I took the wire wheel to the truck on Saturday and ground out all the rust that I could find on both sides of the fender sheet metal in teh rear and on the outside up front. Only in one place was I able to get a couple of pinholes but I had great access to clean this area.
I found the foam you folks talk about on the top of the rear fenders in the double wall area and I didn't seem to have any bubbles in that area.
So I researched my options and then bought a por15 starter kit for 20$ and followed the directions precisely. The por15 lays down really smooth but the rustoleum top coat I used left slight brushmarks. Overall, the glossy black paint where the rust was is pretty unnoticeable against the blue paint.
The por15 stuff directs you to paint over pinholes and that the paint will bridge the holes and stop the rust. I only used like 20% of the small 4oz can of por15 for all four fender lips plus however far I had to chase the bubbles out to find solid paint.
If this doesn't work then I could always pay big bucks to have a body shop cut out the panels. We've got to realize that the whole truck in great condition isn't worth much so these fixes are becoming a reality.
In my opinion it worked great and I hope you all pop off you flares to check on the rust situation. My bubbles weren't yet visible until I removed the flares but if I had waited any longer I would have had major rust issues.