Just got some POR-15. The plan was to slather it around on the frame and underbody rusty spots. The instructions are kind of scaring me a little, the way they call for so much preparation (namely, using their degreaser and metal prep products). Is it really necessary? Or can I pretty much just go for it and get pretty good results? I was also wondering if anyone has used the stuff in visible spots on the body? I've got some rust around the door openings, under the weatherstripping. I was thinking of putting some POR-15 on there, then topcoating with matching touchup paint. Is that a good idea?