next time you go, if you can, get longer ones. youll have a better chance of finding a good arrow and getting a decent spine match.
when i make mine, i use a heat gun with two settings and use the low heat setting. the bamboo will appear to get waxy, then it will be easy to bend. start between the nodes first, i find most bends are actually right before the nodes. turn the bamboo between your fingers horizontally in front of your eyes to help you see the wobble. then when you have the between the node sections straight, then straighten the nodes. these will require a bit more heat, just be careful not to burn them. i suggest practicing finding the right temperature on a scrap piece first to see how it will work.