POR15 would be the best paint for the job. I use it and sell it. POR stands for paint over rust. The base paints are not UV resistant, so you would have to topcoat them if you paint something visible to light (there are a few POR topcoat options). For tow hooks you would be fine, as well as your frame and steering components, since they never see direct sunlight except on the rare occasion you roll the vehicle. There is also a paint called Metal Mask that is a topcoat and makes parts look like original metal, but protected from rust. Check it all out at
http://theruststop.com
Feel free to email me if you have any questions.