Thanks, guys.
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Primer (cont)
Sanding:
some 220 wet sand paper, a sponge and lots of water. I just use a half sheet, fold it in half and sand by hand.
With water, the sandpaper lasts a long time: messy but effective.
I tried something different this time; I put the glazing putty on before the first sanding of the primer to save an extra sanding step. Seems to work well. With the primer, it's easy to see all the mistakes I had with the cloth and resin.
Thus far, got one wing, fuse, flaps and ailerons finished.