Rehabbing a used muffler - SOLVED!

What's the best way to rehab a junkyard muffler? Currently I have a very restrictive puny cylindrical muffler and teeny exhaust tip and I want it gone! I saw this OEM one and it doesn't look badly rusted, just a few spots here and there, and on the pipe, so I couldn't resist for around $35.00. On the other hand, it's been sitting outside for who knows how long.

I gave it my best effort sanding it by hand.... time for the hi-temp paint I suppose, do they make a chrome hi-temp paint? ...would primer be a good idea first?

OMG!! Look at that weak tip weld from just 3 years ago on this aftermarket junk! My fault that I didn't pay attention to what they did underneath. They cut the exhaust flange and welded it there as well... and just as badly rusted! My car hasn't even seen any snow/road salt here in this oven known as central Texas.

From what they told me and what I saw Bobby, it looks like they just cut off the flange and welded it at the point where the pipe ends meet. I haven't driven it today, but I'm about to run some errands. I think it was just a fluke occurence. Maybe the sensor sent a weird signal to the ECU because exhaust back pressure had been reduced from learned settings with the restrictive puny muffler I had?