Wow John! The cage turned out really nice! That should do a fantastic job of protecting you in case of a spill. But the last thing I want is a testamonial from you on that. NO CAGE TESTING ALLOWED !
It looks like you have your work cut out for yourself. I wonder if the idea I mentioned in the PM might work if you start at the back and gently work yourself back out of the car? You could minimize the really tight masking by brushing the areas that are up next to interior panels and headliner. Then do a broad "blanket mask" behind the areas already brushed and spray whats left exposed. This way it would look like it was all sprayed to the casual observer and still have every surface sealed up really good.
Just a thought, good luck.