I used a roller and paint brushes for it. I would not want to spray this stuff unless I was in a booth wearing a full paint suit and someone else to do all of the masking.
This stuff dries very hard and durable, so hard and durable that lacquer thinner won't take it off you skin if you let it dry. It will stick to everything close by if you sprayed it.
It's a thin product and flows out, so you won't see any paint brush strokes or roller tracks.
POR 15 has a whole system for using their product, I just sanded down the surfaces to be painted, cleaned the crap out of them, wax and greased removed and then applied the product.
I don't know how it compares to what you used, some guys in the shops here in Tulsa recommended that I used this stuff, then my jobber at work gave it to me for free (that kind of sealed the deal for me!).
It really is easy to use unless you are lying on your back having it drip all over you. I looked like a Dalmatian when I was through. I should have posted a picture, didn't think about it at the time though.
If you are worried about your fenders, just take them off. they come off fairly easy.