You'll be sorry when you decide to put a nice paint job on. Sanding all those uneven brush strokes out is going to be hard hard work.
If you just want to keep it from rusting and don't care how it looks just wash it really well, let it dry completely then spray on some Rustoleum primer. When you get ready to paint it properly that primer will sand easily and it will give you a nice base.
I once painted my car with a spray gun in one afternoon. I washed it, dried it, masked it and sprayed it. Was it a perfect job? NO. Did it look pretty good? Hell yes it did. Painting a car/truck ain't no biggie.
