- the chemical stripping works excellent especially if they can also do the phosphate bath/rinse
- some places may epoxy prime it for you too, but haven't heard of anyone with a vat of it [primer dries pretty quick!]
- do the stripping before any body work as there'll be more damage uncovered
- I'd use an epoxy primer first, then the best paint your local painter/supplier recommends, partly depends on the look you want
the rusty door bottom isn't just leaky seals, the 'seals' don't totally prevent water entering the door - the door skin is crimp welded and the drains in the bottom plug easily, letting moisture hold in the fine dirt that filters in there and gets into the joint - make sure you treat that area inside, like epoxy primer or a good rust preventive spray - any used TF door you find is likely to have the same problem
Bill