T: I've only done 6 successful ones, so others with much more experience may be able to shed more light.
I use no name spray lacquer on the tubes. I've never had it run. As for bending the parts, I simply drill out a small block of wood with a bit one size smaller than diameter of tube that I'm gluing the parts to. Then, I cut the block down its length, giving me two bending jigs. I just place the gear or whatever over the jig and use a transfer punch to push/bend it into the bore in the block. (I go with a bit one size small because I found that there is some bounce back on the pieces.) It took longer to type this than to perform the whole operations.
I've used both 5 minute epoxy and gel CA glue to glue the pieces onto the tubes. With epoxy, I coat a section of the tube, then push the pieces into it. It's messy, but as long as you use clear drying epoxy, it disappears when you cast the blank. With CA, I just put a small drop on the piece, and hold it onto the tube for the seconds it takes to set. This works well, but gluing your fingers to the piece is a real possibility, since the glue comes up through the openings in the gears. After doing that a couple of times, I went with a pick to hold the pieces in place.
Then, it's just putting the tube into a mold, casting it and turning it to the final size. On some pens where the thickness of the resin between the tube and the final size is small, you need to be very careful not to turn into the brass. After I blew up a couple, I made a point of not putting parts at the very end of the tubes. This way, I can taper down to the final dimension without worrying about turning gears.
I'm sure others have other ways of doing these, and you will be able to choose among them.
