I find it a lot easier to just slap a colour coat on and then work on any issues. You can see there is an issue on the right hand side where the spoiler will go...sadly the spoiler won't cover it so I'll have to sort it out. Other than that issue it kind of looks ok....I have a few sanding scratches to sort out too of course. I find it's difficult to see any blemishes with a matt primer coat...everything always looks great in matt....hence the gloss coat. Am sanding with 400 grit at this stage...I generally use 80grit for rough sanding, 180 grit for smoothing, 240 for scuffing and 400 at the stopper stage. No idea if this is correct but I'm happy with the bumper I did so am sticking with it for now.