I had a difficult repair a few months ago... had it in my head that the low temp aluminum "welding" rod like you're talking about was going to be the perfect solution..... did a lot of research only to find that those rods aren't nearly as special or handy as they want you to believe.
I think when it comes down to it yes they have uses but if there is any way to weld the part for sure do that before resorting to the low temp stuff.
For my project I couldn't find any that was cheap enough to feel like it was worth a try so I tried welding again and fixed the part quite nicely... should have trusted myself to start with.
