Carefully coat BOTH sides of the parts you want to stick together. In this case, coat the fender foam and then the fender. Don't make a mess or get it on your clothes; it is impossible to get out.
Let them DRY to the touch and then say a prayer. You have to pray to the Cobra gods that you get it right on the first stick--because you will NOT get another chance. Once this stuff touches each other in the dry state, it is permanent! You HAVE to push the CENTER of the fender foam in first to stick the center down. DO NOT BRIDGE the center of the fender and expect to push the foam into place up into a hole. It will never stick. I have NEVER understood this. If you put it where you don't want it, you will have to TEAR it off to change positions. If you push it up into a hollow without sticking the center first, it will fall off. This is really one of the worst jobs on the car.
BUT, this is what a really nice job looks like. We actually cut the foam way over sized and then glue it in with the edges hanging out all over the place. We then trim the sides to perfect fit. DO NOT try to fit your foam in perfectly before you glue it in. You will miss and have a crappy job on your hands. You don't have to cover every square inch of exposed aluminum. Rocks are generally only thrown rather straight up.
This is a shot of the top of the left rear fender.
Forward is to the right in this picture. If you look closely at the bottom edge of the foam by the fender lip, you can see we took a small hand grinder and tapered the foam so it didn't stick out so much and look bad. If you are lazy and don't want to trim it (or you really want to have a LOT of fun), just take a few laps around Miller Motorsports Park (or drive up the nearest canyon) and your tire will do the trimming for you.
