Some guys buy rattle cans, I prefer a paint sprayer. Either way will work.
Obviously for a trailer that you'll use to haul wood, you're not looking for a car show paint job. You'd be fine with a cheap paint sprayer. You can get cheap sprayers from HF that run off air, or something like the electric Wagner paint sprayer that I got from Lowes for $100.
If you want to use spray cans, you'll need to buy them from one of the vendors that sells the correct color (such as Rapco), as you won't find spray cans at your local store that match military green or tan.
If you elect to use the Behr Home Premium, the paint codes are all in the thread referenced above. Once the Behr cures and dries, it is very solid. It is not easy to scratch or chip.
Mikey