Cane/boo arrows can be tricky to straighten until you do enough of them to get the feel of it. You need to heat them just enough that they start to sweat. If you can smell the cane, it's probably hot enough. Overheating the nodes is one of the few ways that you can break a cane shaft. Tonkin is harder to straighen sometimes just because it can be very dry after being cut and packaged for so long. The easiest method for me is to straighten each section between the nodes individually first. Ignore the whole shaft and get each section perfectly straight, then straighten the nodes to line all the straight sections up with each other and you will have a perfectly straight shaft. Be sure to let each section cool before you work on another spot, or you can unstraighten it if it's still warm. I like to take the nodes down even with the rest of the shaft, myself-but do that after you have it straightened.