Electra / Sabre Jet wood wing

After the brushed-on coat of "Prima" has cured, the task of sanding it off also acts to sand off and make flat the 2nd coat of resin.
A dual action orbital sander (set on low speed) such as shown really reduces the time to accomplish the task. Use #180 grit sandpaper and keep the power tool moving. Do not attempt to finish the contours of the tip and leading edge.

After removing about 50% of the grey "Prima" switch to a flat hard (1/4" ply) sanding block with #180 adhesive back paper. Work with the flat block until only a few traces of Prima remain, then use a 3M #20 sponge pad (3M part # 05526) staying with the #180 grit paper.
Whatever Prima remains is in the low spots. The 2nd sprayed-on coat of Prima should even things out.