With the utmost respect to Ulf and other DIY'ers on things like this (there was a recent posting on the restoration of some headlamp part using the aluminum from a downspout strap) who try and engineer these solutions...
...at some point in the future, an FO (that would be "future owner" as opposed to "previous owner") will look upon this and cringe and shudder. "What was this PO thinking? ... I can't believe this work... Now I have to re-do it."
An independent inspection, or PPI, would yield comments about inattention to detail or poor maintenance, bad body work, bad painting and more. If they did THAT so badly, what else did they do? Or, if a car brought "here" for review, it might very well be torn apart like vultures on road kill.
My opinion only: Ulf, don't waste your money on the paint. Let a pro do it.