There are shortcuts and there isn't anything wrong with them, like POR products. These products get the job done. There are so many different levels of 'getting the job done' that its hard to place where POR or Eastwood equivs would place.
If you want a truly superior job, and the technology has changed dramatically in the past 10 years, you will want to go with the newer Epoxy primers after sandblasting and metal prepping the surface. Once epoxy primer is applied, urethane high build to solve any imperfections, epoxy sealer, then topcoats (either single stage urethane, or Basecoat/Clearcoat), also Urethane based.
POR 15 and the like are great if you don't sandblast, but rather just wire brush the rust and crud off the surface. Some people don't have the ability or inclination to sandblast, thus why the POR products are popular. These are the guys that boast that their trucks are a '20 footer'.
The problem with not sandblasting to the bare metal is that chemicals like brake fluid (Or grease etc) that permeate the metal and will stay on the metal even after the POR or whatever is applied. Now you have an accident waiting for a place to happen. Just not worth it. Even if you are a POR fan, clean with at least PPG DX-330 very well before applying. If its not blasted, that wont even work since the rust layer absorbs too much of the bad chemicals and will always be present until you blast it off. Chemical stripping is an invitation for that chemical to seep into seams where you cant clean it out, thus leaving a dormant chemical just waiting to ruin your paint job a few years later from the inside.
Whenever I hear someone chem stripped their truck, and the paint job looks really good, I just look at the cab rain gutter and there it is.. bubbled paint that will be noticed by the owner a few months later.
No question, POR products have their place. And they work WELL if the metal is prepped properly first. Sandblast, apply epoxy primer, then POR 15 and all is as you could expect. It isn't the way any painting professionals would suggest, but its cheaper and a way for novices to get things done. If you listen carefully to the auto paint professionals, none of them have POR products or anything like them in their arsenal.
