Yeah, muffler cement isn't the answer here, thats more intended to seal joints between tubes, where one end is flared to slip over the other. It has no real structural strength and doesn't bond well in surface applications.
I'd try JB Weld before I even considered that stuff. But, I wouldn't use JB Weld either!
By all means buy the welder and get to playing, it sounds like you really want to anyhow! Just practice a lot on various materials first, as suggested by others above. Leave the mufflers alone for the time being, there's no really effective alternative. After you've laid some beads you'll be better able to judge whether you can repair your mufflers, and picking up a new skill (and tool) is rarely a bad investment.
mystic_1