I believe that maybe someone has taken "sweating" just a little to literally and maybe I should have mentioned "brazing" but this rod is similar to some that a friend uses. This is a very short video and you can see the quality of the finished seam.
https://www.youtube.com/watch?v=LMNBqDtzI9Y
Take a look at their SSQ-6 paste.
I'm quite sure he doesn't use the MuggyWeld product but he could very well use it.