Charge per opening. On small jobs figure the number of trips and time you will be there plus material, + material MU.
On a small job like a bath remodel you might go out for the demo work, rough, finsih the rough because you had to wait for something, trim, go back because they were missing a light, etc. You end up with a lot of drive time and not many openings. That's when you need to figure in trip charges hidden in your total.
Tom
