which one is correct way to enter tasks?

1-entering a tasks duration, even if you know the total amount (say sf) of the task and how many people you will assign to it,

or

2-just entering the square feet of quantity, and the units (labor) that will perform the task, and let project calculate the duration.


lets say I have 500 sf of wall to paint. I know this for a fact. I have 2 painters who can do 100 sf everyday. I know this for a fact too.

based on this, do i build my schedule like in 1 or 2? which is correct way?

also is there a way to enter 400sf for the total quantity of work? can work be sf i mean?