Auto body repair & detailing: 55 Chevy 1st series P/U, ticking time bomb, 55 chevy

Question
My son and I are working on a 55 chevy p/u. Someone before us had done some repairs on the body which was really good, but it rusted under the bondo. The rust didn't go through the fenders, but did pit it around the wheel opening. NAPA sold me some stuff that I'm suppose to spray on and let sit for 24 hrs to kill the rust. My problem is that there was any where from 4 to 6 layers of paint and primer on the fenders. I ground down to the metal and sprayed the stuff on. The fenders turned black where the rust was, but now since the paint was so thick, I'm having a hard time trying to blend it in. I had to put some bondo glass on the fenders in areas where I ground down to the metal because I had to take bondo off. Is there a way to get the bondo glass to match up to the paint? I mean, is there a secret to getting everything even so it doesn't look like a wavy fender? I know that the ideal thing would be to take all the fenders off and strip the paint off, but the only areas that are really bad are near the wheel openings. Any tips would be appreciated.
Thanks
Ron

Answer
Ron, there is so many things wrong about having 6 coats of paint on a panel that you just wouldn't believe it. A seventh? It's a ticking time bomb, one that is surely going off as we speak. About all I can suggest, since you have a real aversion to doing this right, is using UCS's Icing P.N. 26006 as a skim coat filler to bridge the low area and bring it all up to grade.