You are on the right track. Put a layer or two of 2 ounce cloth on the plug soon, and do all of your final sanding after that. Get some laminating resin. Minute epoxy is junk. Use the resin you get to make your finished parts with as well. Finish your plug with primer and sand as necessary to 1000 grit. put 6 to 8 coats of mold release wax on and coat with PVA. Your plug is now ready. A 1 piece mold is easier if the shape will allow removing the plug.
For the mold, coat the plug with resin and lay 2 layers on .5 ounce cloth. Follow with 4 to 6 layers of 2 ounce cloth, and finally 8 to 10 layers of 6 to 8 ounce cloth. Cure for 3 days and remove the plug. Cure the plug for 1 week. Wax 6 to 8 coats and PVA. Pull your first part, wash the PVA from the mold, apply PVA fresh, and pull another part.
Scott