I’m doing a frame off restoration of my S15…sentimental value…Looking at my underside of the cab, I see remaining undercoating, which looks old, dirty, etc. We have cleaned it up as far as grime, etc. I’m debating on removing the undercoating with heat and a scraper. From what I can tell so far, there is no rust, except for a rocker panel, which we are going to fix. Where there is no remaining undercoating, I see what I believe is gray primer…I’m not sure about what to do once the undercoating is removed. If this gray looks good, can I leave it on there and spray undercoating on it? I’m concerned about keeping rust away and longevity more than cosmetic appearances since this is the underside. Or…my husband and another guy advise to soak this undercoating in gasoline, which will soften it up…then powerwash whatever will come off and then apply new undercoating over the remains. They think the undercoating still looks pretty good… Is there another way altogether??? And…should the rusty rocker panel be fixed before I work on the undercoating or does it matter? Thanks so much for any advice you can give me!!!