unfortunately, i dont really know how to terminate the knot well
the entire thing is tight enough that were i to try to slip the cord under the wrap, or try to place the end strand through out the entire thing (like the first step in a strider style wrap, so that a strand is running down the length of the handle under the wrap), it would make a very noticable bulge, and be impossible to keep straight during the tightening process.
i basically do a simple single knot, as tight as i can get it, sew it shut, and then burn the ends so they mix with the rest of the paracord.
because of this, i havent tried doing any of the multi strand turks head, just because i dont know what to do with the ends
the knives in the photo are a forum members set of busse combat pure bred fighters. the 4", 6" and 8" models that were sold unwrapped.
as far as how much cord length is required, and how to judge it, i tend to do a really loose quick knot and then judge it from there. on these it took about 2 arms lengths (12 feet) fully tightened, but in an untightened state it was 14 or 15. i basically used 3 arms lengths and then cut off the remainder.
this specific knot had 5 spirals (5 x's total on the first set of rotations), so i guess the 4" pbf (wich had 4) would be a 16 lead, and the 6" and 8" would be 19... i need to run through my ashleys book to become better aquainted with the terms. id say that its an overal moderately easy knot to perform, but a very, very difficult knot to tighten.