Tip: Paint your Ceilings first!

I would save the masking to mask the ceiling before I paint the walls. If I mask the walls to paint the ceiling, I need to perfectly match that mask line when I mask the ceiling to paint the walls. There is no reason to mask twice. Just paint the ceiling with some overlap onto the walls then mask the ceiling and paint the walls and paint over any ceiling paint that got on the walls.

If you want to have a good clean and straight line at the wall to ceiling, use some painters caulk to create a smooth joint between the wall and ceiling, let it dry well than paint the ceiling and the caulk line, let it dry completely. Then, mask the ceiling at this caulk line and paint the walls.

Personally, I would never do multiple light coats. A good wet coat means the paint polymers are continuous versus being in 2 or 3 thin layers. The paint also cures better when a properly applied coat dries. So, follow the directions on the can of paint. It usually says a good wet coat. Just avoid drips and runs.