Yup, I used that cold galvanizing as a primer, then whatever I have for paint. Once I get this rear section of frame done I'll brush on some Armorcoat primer first. I've found that brush on last 5X longer then any spray can... just doesn't look as nice at the start. For your truck, you may want to get a quote from a dealership, or a reputable body shop. It may not be as much as you think. Another option would just be to wack the undercoat to the rusty spots. I like Rust Check but their are others.