Zgrip is great stuff. Sands easily. I agree with ^. First thing I noticed is that your body line isn't as sharp and it will be very noticeable. If I can see it in a picture in primer, it's going to pop bigtime in paint. Also, are you using rattlecan primer? It would make sense for you stop doing that and prime each panel with a good epoxy primer. Many paint companies don't approve of that type of primer under their topcoat. Just trying to save you some trouble.