Exhaust repair question

I seem to have some leaks before and after the muffler that was welded in while the PO owned it. I don't have the $ for a new cat back exhaust. I tried using JB weld on the manifold at one point on my last truck and the heat just cooked it like a steak on a grill.
Would the exhaust back at the muffler be cool enough for JB weld to work? The exhaust noise got old 7 months ago, looking to fix it soon. thanks.

See what you can find at the junkyard if you won't/can't fix it properly.