I found that bushcraft lanyard thread you're talking about. Pretty slick!
http://www.bladeforums.com/forums/showthread.php?t=634900
It looks to me like what he's calling a "barrel knot" is a mini hangman's noose or a loosely tied "Chris Reeve" style lanyard w/ just a few turns and a long tail loop. I just tried it, and it looks the same as the picture. You could tie it with any sliding knot like an overhand knot around the standing end ("simple noose") or a double-looped overhand knot ("poacher's noose"). Just be sure to tie the knot close to the lanyard hole/knife like he says, b/c when you tie the two ends together to finish the lanyard, only one strand will slide when you make your adjustments. If you think of it as a figure eight with the "barrel knot" as the middle and the two loops as the two loops of the eight, you want the knife end loop to be small, and the wrist end loop to be loose enough for easy use, but not so loose that you have to adjust more than a couple of inches. Only one side of the loop will adjust, so the over hand knot at the end will sort of travel around the loop a bit... too much and it could cause a hot spot in your grip.
Once you have it in your hands, it is much simpler than all these words.
Here are some links to a couple knots for reference:
noose (simple overhand noose) down on bottom right:
http://www.animatedknots.com/truckers/index.php?LogoImage=LogoGrog.jpg&Website=www.animatedknots.com#SlipKnot
double overhand noose
http://www.marinews.com/Double-Overhand-Noose-723.php
hangman's noose:
http://www.marinews.com/Hangmans-Noose-362.php
Just leave yourself lots of extra cord on the working end (the end you wrap around), then size the loop, tie an overhand knot with both strands together as the end knot, and trim below it.
Pretty cool idea. I usually only see lanyard knots that are either a fixed loop or have some kind of cord, wood, or bone woggle (slidey thing) on them.
