Here is part of the instructions that came with the kaoko that's made specifically for barkbusters. It's KAO.KBB700-S for the kaoko and BHG32 for the barkbusters.
You can see in Picture 3 that the "thrust washer" is on the left, then the knobby part of the kaoko, the friction nut, and finally the barkbuster.
Initially, I thought the thrust washer goes under the throttle grip. That's the way my throttlemeister worked on my sportbike. Now, I think it's the 5mm washer shown, which is used on the R1200GS. This was the source of my confusion.
The kaoko bar end is pretty lightweight. I may revisit the duct tape and wheel weight idea, like when there's two feet of snow on the ground and I run out of stuff to do.