Looking for some advice regarding sanding techniques during touch up paint application. Specifically, I’m working on a few small stone chips in the hood of my Audi 2018 RS5 (color Nardo Grey). So, far I’m finding it difficult to get the paint to “adhere” to the primer layer - even after letting is dry for a week+ before polishing. I’m thinking about gradually layering the OEM paint, and sanding between each layer to improve the probability of it sticking. Any advice in terms of techniques, or sand paper grit count, etc.?