I noticed that, but found some old solder! My hoarding knows no bounds!!
Thought so, that's why I mentioned it
A great example of negative progress, more difficult to use and to what purpose, I'm not aware that solder vents lead into the air or the water courses to any significant extent. You can still get leaded solder from plumbers merchants, with the warning that it is not to be used on potable systems. Tends to be a bit thick for electronics work though.
If joining the braid, then I suggest flowing solder onto the braid first and then joining.
If you are just onto a heat sink then get some solder onto the heat sink first, then try soldering onto the blob