My exhaust pipe is painted black and I had to bend it. I have a good propane torch, but it didn’t put out enough heat to get the pipe hot enough. I had to use an oxyacetylene setup with a broad, hot flame similar to what I use for brazing to bend it. Either torch got hot enough to burn the paint off the pipe, so I had to repaint with high temp paint.
I tried to bend the pipe cold first, but couldn’t get enough leverage on it. I might have been able to if I made a jig so I could clamped a length of 2x4 to it, but the torch was handier.