Interesting. That car i posted above, he actually did POR15 before he put that undercoating on. Here's what it looked like with just the POR15. I have no idea about what these coatings are, so I kinda figured it must have just been kind of a primer or rust inhibitor or something.
Only thing I don't like is how shiny it is. I think more of a matte finish would be my perfect world. But i'm open to anything at this point really.
I'll try to wash it and get it as clean as I can, but I'm not going to sand it down to bare metal. So if there is a product that will adhere better than others with a surface that's just been washed (not sanded), that'd probably be higher up on my list.