I use Wil-Bond on anything I paint. I used it on the undercarriage of my truck before I undercoated and the stuff never even chipped. I've even used it on surfaces that are supposedly unpaintable (i.e. vinyl window trim) with excellent results.
At this point I would tell you to sand/remove as much paint as possible before prepping with this stuff, maybe a couple of times to really etch the surface good.