You don't want to heat the aluminum unless you have to. Aluminum goes from annealed to a puddle very quickly.
When I installed rub rail in years past, I attached it (with pop rivets) as I worked my way around the boat. When you come to a sharp corner, you don't want to stop bending it in the middle of the corner. You want to work it around the corner very smoothly and quickly. After you stop bending it, it's work-hardened and it doesn't bend as easily. That's the point at which you would need to take a torch to it. But you want to avoid that if at all possible.
You want to plan your starting point so you don't have a a joint between two pieces near a corner. You'll need the leverage of a piece of material hanging out there to be able to effectively bend it by hand.
You shouldn't have to worry about kinking it.
Good luck.
