My advice is just to focus on getting them together correctly at that point and make sure the angles and curves are right. It's extremely difficult and there will be glue or resin everywhere but you can clean it up later.

A part of the traditional technique you might be able to use is how to apply the gold. They use a fine gold powder, but it isn't mixed into the resin. Once the crack is fitted and set it is painted over with resin again and then gold dust is sifted onto the resin before it cures. This ends up looking a lot smoother and better than leaf or gold mixed with the resin. There are some techniques where dust is embedded into it then sanded down but I don't recommend them for starting out.

Honestly it sounds like you're doing fine. That sort of experience is consistent with how I learned, it took about a dozen attempts before I got anything worth showing anyone. Like I said, it's a difficult, frustrating skill.