Spray gun works a lot better than brush and I think looks better. Painting is easy, its all the prep work that takes time. It all depends how nice you want it to look. If you are going to do the whole truck on the outside, 2-3 gallons would be good. if you are doing 3 color camo, I would get 2 gallons of 383 green, one gallon of 383 brown and one gallon of 911 black. To be extra safe, you could get one more gallon of 383 green for a total of 5 gallons. I don't like running out mid project or feel like I have to cut quality coverage to save paint. That is just me though.