I seat GC prior to coating. If you find you have under-sized shanks, it would make sense to coat before seating checks. But most shanks have a rather generous girth in the first place. Some general observations I have made, with coated bullets in bottle-neck rifle cartridges:
- coated, GC bullets often shoot well with starting loads for jacketed bullets, using the faster of the listed powders. Sometimes slightly reduced.
- Coated PB bullets often shoot well with loads similar to what you would use with a lubed, GC bullet of the same construction.
- Bullets designed for GC often shoot well without GC (bare shank) when coated. Particularily bullets with a reasonable bearing surface despite the absence of a GC
- Due to slight variability of coating thickness, don’t aim for «jam-fit» COL, unless you uniform the nose after coating with a swaging process. You’ll get some cartridges that’ll refuse to chamber. Use enough jump, to allow all cartridges to chamber without resistance. With a short jump COL, some cartridges offer resistance when closing the bolt- and result in (often) a high flier. Use enough jump, the bullets can take it.
- Bore-riders that are well-fitting in the first place are unsuitable for coating. Generally, bullets with conical noses are best.
You’ll find there is a little learing curve related to this technique, but you’ll get the hang of it in a short while. Just be prepared for some frustrations in the beginning (I sure had).
Good luck, and happy shooting!