If you plan on making a plug, I would add all your panel lines and details on the plug using one of the more popular techniques. Most common method is to make the details in primer. For butt joint panel lines, use 1/64" chart tape. Once covered with primer, you peel the tape up leaving a 1/64" wide line the thickness of the primer coat. For lap joints, you place painters tape on the part to be the lower panel, and build up primer on the high panel. When you remove the tape, you have the step simulating the lap joint. To add flush rivets, use a 1/32" brass tube attached to a soldering iron to melt the rivets into the primer. To add dome rivets, use a syringe with thinned wood glue. Once done, wax and polish and make your molds. When you make your parts, give a light coat of epoxy to the inside of the mold to capture all the details, then do the rest of your layup.