I built boats for a while in the '80s and used a lot of West epoxy. They are still around, obviously, as are competitors.
The drill was: bare wood to start is best. Otherwise be sure no grease, i.e. wash with acetone. Thin coats are preferable to thick. Resin can be applied with a disposable real bristle brush, or with a flexible plastic squegee. First coat to soak in. Wood and resins should be warm, in the 70s F is best. As the resin soaks in little bubbles will appear, pop those. After cure (overnight in a warm room) sand the first coat down to remove the raised grain but not smooth. Second thin coat to complete filling the grain. Cure overnight. Wash with warm water to remove "amine blush" surface film that appears. Sand carefully to smooth the epoxy surface but don't sand through it or you will have to start over with the bare wood spots. Third coat to level and make a hard surface. Wash, sand, and shape the third coat.
If you want to add a thin layer of cloth, something like 2oz, add it dry after the first coat while it is still damp and squegee another layer of resin on from the top, wetting the cloth that way. I'm dubious about the need for this on a bass, actually.
On a bass neck, you need to take the neck off the bass and mask things very carefully. You need to remove the masking tape each time, taking the tape off when the resin is "green", meaning partially set and won't flow anymore, but not completely set. The epoxy can saturate the tape and if it cures that way the tape becomes a permanent part of the neck and needs to be sanded off. Re-tape for each coat.
I am sure some progress has been made in coatings since the '80s, but the process is still the same as far as I know.
The other way I have heard to do a bass neck, I think maybe on Mike Lull's website, is to mask the sides and bottom of the neck and leave the tape sticking up above the fingerboard. Level the fretboard, pour a bunch of epoxy on (one thick coat instead of three) so there is a very thick layer, which you then shape basically from scratch the same way the wooden fretboard was shaped in the first place.