How much paint?

[Billybob]

Hey guys, I'm spraying a 17 Mako with Awlcraft.
Have a gallon of the 545 primer but wondering how much we need for the colors.
Waterline to rubrail will be gray.
Cockpit/ console/deck will be white, but the non skid areas will be kiwigrip.
This stuff mixes 2:1.
I'm wondering if anyone here who has done an 18 or even a 20 could give me some guidance.
Don't want to buy more than we need, but certainly don't want to run out either.

Thanks