I spread the glue with a brush, word of caution is that the glue has a high amount of solvent in it so as well as having good ventilation while using the glue, it will also cause the BK5 to 'pucker' if you apply too heavy a coat, test on some scraps before you go whole hog with it to get the feel of what it will be like.
I didn't do two layers of the BK5 because I'm restoring a Kodak 2D and i wanted the red bellows.
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