I have been using BLO on most pens as a first coat before CA. What should I use, or is it ok to put CA on bare wood?
Gotta be careful - the CA police will nab you if you do it wrong.
Seriously, you can do anything you want.
I'm not a great fan of a CA finish, but I go admit that it's effective on pens. In my experience, applying BLO first helps bring out the grain, and having a bit of BLO on the paper towel certainly help smooth out the first couple of coats of CA (which in my case are usually thin). But subsequent applications are medium applied with a plastic bag.
But you can certainly apply the CA to bare wood, either as a finish or to stabilize the wood. I'm working on a hand mirror in cherry, and the wood I have has some cracks. A few minutes ago I roughed out the shape, and then put some thin CA directly onto the wood in the area that is cracking. The CA will be drawn into the cracks to prevent them from getting worse (I hope). After it cures, I will go back to finish off the shape and start sanding.