questions about right after paint is laid

If the car is going to be painted in a paint booth w/heat, you can mask it off the next day just to be safe vs. that same day if need be also.
Laying clear plastic down the next day won't hurt even if car is not baked at 140 degree's for 2 hours or less. Just don't apply pressure to plastic to much and you'll be fine. I paint for a living, 20 + years, so I wouldn't steer you wrong. Besides, your painter should have this answer for you as well IMO.
Can't wait to see photos of it done, always exciting!

Mark