For the early Brad Nelson phasers I need to hide the epoxy line. I use Bondo red finishing putty. It is only for this type of work or flea bites. I’m warning about this because I worked on a Brad Nelson where this was used as a repair putty. The P1 was repaired on the bridge between the meter, ready light and on/off wheel. It failed while I was working in that area. It has no strength so remember that. There are four sanding lines on all BNs, remove them. The side ribs and rear fins need detailing. I keep broken tip Xacto blades for this and similar work. The small chisel edge is perfect to deepen the grooves. After you are satisfied with that, round each of the three pieces on the ribs and the four on the fins. This is a slow process, an hour or more but worth the final look.
After you are satisfied use a Bondo tac rag to remove the dust. Spray the first light primer coat. Let it dry overnight. More finishing putty will be used later on any imperfections.