Mine is going to paint with the entire power train in, dash out, and doors, fenders, and hood off. My body guy will then install all the body panel and line them up, then shoot the clear coat. after that, install weather stripping, and back to me . My engine compartment and undercarriage are already painted.
Also, if you do this, make sure you run the engine and test for leaks. All I will do when I get the car back is bolt on trim, bumpers, lights, windows etc.
No matter how careful you are, it is too easy to scratch/dent/scrape new paint when trying to install the engine. Plus the hood has to be off.