It depends on too many things to answer easily. What kind of finish are you trying to achieve? Are you pore filling? What kind of wood are you using. How many sanding sessions will you do? Are you using a sealer coat? Behlens spray isn't exactly the same stuff as what is sold in the cans and I have no experience with the aeresols. I'm guessing a couple of cans should do you if your prep work is good.