Thanks for the detailed response! I can't imagine getting 8 blanks done with one batch of 5 min epoxy! Your process sounds much easier than mine!
I've been using the JB Weld 5 minute epoxy for a while now:
A crystal clear epoxy formula that sets in just 5 minutes—includes a mixing tray and stir stick.
www.rockler.com
Its gotten thick in the cold, so I try to warm the bottles up with a lamp for a while, or just bring the bottles in so they don't stay out in the cold shop. Anyway...in the hottest part of summer, you might run into the time limit, but in my experience through most of the year, a 5 minute epoxy is workable plenty long enough to slip 8 tubes into 8 blanks.
I've been working batches of 5 pens at a time with Sierra style pens. I spend 30-40 seconds mixing, till its really good and mixed. Then roll my tubes in, twist them into each blank. I use the next tube to scrape off the excess and put that back in the pool of mixed epoxy, then use a q-tip or popsicle stick to push the tube out through the other side. Apply a couple dabs of epoxy there, twist it back in, scrape off the excess and wipe the inside of the tube clean with a q-tip. Once you get the pattern down, you can put a bunch of tubes in a bunch of blanks pretty quickly.
I find that this epoxy doesn't get runny. I have used it in the shop with it up in the high 80s, and it always seems to be pretty sticky stuff. There is always excess that comes off the tube when you twist it in. You always need to clean that up, with any epoxy, in my experience. Either the next tube, or a popsicle stick, will do the job. With a stick, I tend to split the excess in half down the middle, scrape it off to one side, swipe that on my wax paper next to the epoxy pool, then scrape off the other side. That tends to leave just a tiny bit of epoxy on the inside of the tube, which I clean up with a q-tip. You can also keep the epoxy on the stick, then push the tube out the other side of the blank, and just apply the excess there as well. Its good to do that, to make sure that both sides of the tube are well glued into the blank...otherwise, the first end of the tube you insert will often have little glue (it mostly gets rubbed off onto the inside of the hole in the blank), and you'll have a weak bond there. I usually use a glove on my right hand when gluing tubes...inevitably, a bit will get on your fingers. I tend to reuse the glove over and over until it starts to tear, though, to minimize the cost/waste there.
I generally leave them overnight for a solid harden, but I don't think you really need that long.