I’m rapidly approaching the point where i paint my pack, but i’ve been concerned about the paint getting into certain nooks and crannies, mainly the top of the pack. I was just wondering if its easier to spray the ion arm and booster tube and then attach them rather than attach them and spray it all at once?
Yeah, it’s really much more easier to get paint evenly into every groove when the parts are separate. I am at the same point, the final base coats are nearly done, and the final cats are waiting next. Now, my pack is in one piece, and I did find it difficult to paint the top portion of the pack evenly. Therefore I suggested to my friends that they did NOT glue the parts together BEFORE they are painted. Much, MUCH easier to do. Nick-A-Tron’s pack build shows this quite well, although he went so far as to pant and weather the pieces one by one.. The only problem with painting separate is that you need to consider that the glue will not hold on to the pack material it self, but rather to the paint job. Therefore it is possible that the hold is not great. To circumvent this, you could mask the areas where you are hitting the glue on, thus keeping it clean as you paint.
Each method has its pros and cons. if you spray them first and then attach them it will be easier to paint but then when you glue them on you will have to sand away the paint where they ion arm and booster tube join to shell as to get a strong bond.
if you glue them first the bond will be strong but the parts will be harder to paint as there will be nooks and crannies.
what i did with the pack im working on now is glue the booster tube on as i had to add the “weld line” with 2 part putty and that had to be painted too but left off the ion arm. I then used a brush and some black to hand paint the undercut of the booster tube and the part of the shell it was “hidding”. Then i sprayed everything including the ion arm. Once the spraypaint was fully dry I added the ion arm. As i used a wooden block screwed to the shell to mount it i wasnt too fussed about their being paint at the join but I did give the area a little sand just to rough it up a bit. glued and screwed the block to the shell and the ion arm to the block. No area left unpainted 
Well thankfully the booster tube i have is black already, but i know what you mean about the epoxy putty, mine dries green. I was intending on doing the weld line too on the booster and also the welds on the ion arm, also using the epoxy to attach it to the pack. What i was gonna do after it all dries would be using a Sharpie marker, just colour in the epoxy black. Sound like a good or ■■■■ idea?
You’ll probably fin it much easier to make the weld lines after the epoxy has set a bit, but not fully dry. If you let it dry, it will be a hard job trying to get a decent job. After it has dried, you can paint it with ease..