On the ones we've done like this before, we've just backed taped with fineline tape and have never had any issues. As far as the door post, those areas like where the fender meets the rocker and such were not sprayed. They were taped up except for the top of the inner fenders. On top of the inner fenders is just a light coat of bedliner spray, usually don't have a problem but if so all it takes is a little grinding with a flapper wheel.
Thanks for all the comments so far, I think Lockjaw is finally seeing some progress on it.