So, 'tomorrow night' was in fact the next night. I am just now getting to uploading the pics and telling the story...
Gluing these blocks onto the flamethrower wouldn't be good enough for me. I could easily see an errant door swing knocking one of these off of the flamethrower. So I decided to reinforce the bonds a bit, by 'pinning' them into place. I drilled a couple holes into the underside with a small model-making pin vise. I have a bunch of scratch-building brass wire around, and it fit the bill perfectly for this job. I snipped off a couple pieces.
After mixing up a batch of JB Weld, I dipped one end of the brass rod in and stuck it in place. The holes I drilled are a little oversized compared to the wire, only so I have some positioning & 'wiggle' room when doing final assembly.
Pins are epoxied in place...
...for all the blocks. I also drilled corresponding pinholes in the black block on the flamethrower. To do this, I 'eyeballed' the position of each pinned block and simply pressed down. The pins made marks and dents in the paint, which I drilled the holes through. Once this drilling was finished, I mixed myself up a batch of DevCon Plastic Welder. Notice that the undersides and mating surfaces of the parts have been scraped of paint all the way down to bare resin. This is so the Plastic Welder will bond to the resin and not the weaker-bonded paint.
Ta da! One finished flamethrower. Hope it passes muster here on TDH!

As for the whipcord launcher, I used CA/Krazy glue to glue the plastic cutouts to the sides. I had some styrene strip (used in my model-making) that I cut up to use for the 'front' of the whipcord launcher, also attached with CA glue. As well, the leftover JB Weld was used to epoxy the BBQ lighter (see many posts previous for details on that) into place.
Here are the finished pieces. The whipcord launcher has the nubs on the back end of it. They are supposedly late 70's era dental files. There is a TDH member around here who still has some if you're interested in buying the real thing. In my opinion, it's just another easily snagged and lost piece of the costume during a troop. I elected to leave them as is (for now... :rolleyes )
I painted both of them with Citadel Paints Chainmail from Games Workshop, a miniature wargaming company. The wrist-most one got an overcoat with Citadel Mithril Silver, while the elbow-most one got two coats of Tamiya Clear Red.
Cheers!