I used this paint/primer on my SHO's engine bay, rocker panels, fender wells, sub-frame and I’m really impressed. I definitely recommend this product. It's a little expensive but well worth it if you are looking for rust free. I had it on my cars for about 4 years now and still looks new and rust free. 
Here's a video I found on youtube with a demonstration of the product.
https://www.youtube.com/watch?v=bWnqHVFl7Ng
Here's a video I found on youtube with a demonstration of the product.
https://www.youtube.com/watch?v=bWnqHVFl7Ng