I used white primer with my Gloss White paint job. I kept accidentally sanding thru to it, and it looks gray compared to the bright white color of the Rusto main coat. I can imagine that red would be a nightmare to try to cover up and that if you ever accidentally sanded thru to it, there'd be no hiding it.

If I had it to do over again, I'd use no primer at all, except in areas where I had used bondo. The reason is, if I'm gonna sand thru to my undercoat, why not sand thru to the color of your main coat instead of sanding thru to some primer that's a different color? In other words, why waste your time with applying two layers of primer when you could have an extra two coats of your main color instead?

With this paint, I really don't see the point of using primer.