I have taken to using thin CA for BT reinforcement. I apply the CA directly (and CAREFULLY) to a cotton swab, then wipe it around the inside of the tube. Depeding on tube size I might do a second application to get about 1/2” coverage at the tube end. I find the thin CA tends to soak into the paper better, rather than coating it, as medium CA tends to do. Still need to sand it out, though, if for no other reason than you want it as smooth as possible.