I've been using SEM Black Trim spray paint for renovating the elderly rubber and plastic on the exterior of my 25-years-baking-in-Arizona-sun car. Just wanted to recommend this as an excellent product ... for example, I sprayed the front 'smile' about a year ago and it still looks like new. I've seen only 5-star reviews for this product.
The flip side to a rusted-out car from Michigan is one like mine, that's been baked and really should have the rubber bits replaced. I guess that's better than rust, though.
Although come to think of it, you could also fix the rust with spray paint!