Well, I played with this stuff a bit and think I got a good result.

I used a small paint brush to dab over the pinholes. The liquid coating they send you is pretty thick and after about 4 coats everything is light-tight now. I avoided the fabric since the holes were so small. Worse comes to worse, I can reapply with fabric. Of course my grey bellows now has some black specks on it, but this is not a beauty contest (which a CC-401 would never win anyway).

Of course now this beast is sitting in my living room on top of my Benbo like some sort of sculpture waiting to dry.....