I use Gunze Mr Surfacer, dolloped on with a brush. It dries quickly, then sand. It feathers out beautifully. It works so well that I can relax while scribing. I used to find panel scribing nerve wracking, especially tricky corners, for fear of a slip. Now, knowing I can easily and seamlessly repair any slip, I don’t worry about it. This allows me to scribe with confidence, and being more relaxed I found I made fewer slips. Win win.