I plan to undercoat my rear wheel wells tomorrow. The stuff that replicates the original is 3M body Schutz. You need a specific gun to apply it (which I have) and it will have that popcorn look (for the lack of a better word). The schutz stays rubber like I believe like the originals stuff. Someone also commented to me that the front wheel wells did not get the schutz coating.
There is also another product called Wurtz that is a clear wax like coating - this coating drys hard and can be painted over, but I am not as familiar with this.
