I use a hot knife also. I pour a dozen of black and a dozen of blue senkos . Cut the tail off all of the and weld the opposite color on all. I use a little " bump board" with a mark to keep them all the same size. Once you get the hang of sliding them together it works great! I put the hot knife in my vise so I can weld them with two hands. There is a video of this out there somewhere. It's on a post a few years ago.