I did quite a bit of testing with this stuff for waterproofing and the problem is that it's actually pretty porous when dry. Even multiple coats where not reliable. Sealing the pores with a few coats of ca glue helped, but was still not enough to trust with anything important.
Dave's method of wiping vs dunking worked very well for me. If you want to add a layer of safety, you could apply bees wax around the bolster area