Neither my local hardware store (O'Connors in Billerica) nor my local autoparts store (Bedford Auto Parts) stock POR-15 (nor had the guys heard of it), so I've looked it up on the web. The Porstore site has all kinds of instructions that lead met to believe that it's a lot of work to use this stuff - soap wash, phosphoric acid wash, humidity control - but you're suggesting it should work well without much ado.
Honestly, I think most of that stuff is just add-on. Guys have been using POR on Porsche 914's without even bothering to clean the metal. Oddly enough, the rustier the metal the better it will stick.
Buy six of the little cans, and use one at a time. Simple rules: 1) Surface should be brushed clean at least. Dry is important. 2) Don't get any water in the can. Even sweat will wreck it. 3) Use a brush you're going to toss anyway4) Do it in 2 coats, 4-6 hours between. In the meantime use a piece of saran wrap between the lid and jar.
5) Wear gloves. If it gets on your hands it will be there for several weeks.Other than that it's pretty neat stuff. Regular is more than enough, topcoat it if it's exposed to the sun (the snow chute is not exposed to sun)
Chris