The bubbling will probably be where there is galvanic dissolution going on causing the bubbles on the paint. So if you can get in behind the door panel for example make sure its really dry, peel back the aluminium from the steel carefully and stuff this area full of waxoyle and then seal it all back up and blast more on so any water won't get in and start the reaction again.
If your getting this anywhere else see whats on the other side, if its just a dodgey bit of paint, rub it right down to bare metal and give it a spray of primer.
I would rub the steel back to bare metal, then I would get the best primer I can find and get that onto the bare steel now so it has a chance to fully set before getting the top coat. The painter will then be able to work on that.
I would also do that to the metal sills along the top of the tub as well while your at it, because there would be nothing worse than if you got it all sprayed then they rusted up and started staining your new paint with rust lines.
