Oldster,
I'm not a bamboo rod builder or restorationist but I'll offer some advice as I have been down this road.
Most folks will use steam or a heat gun to straighten a tip section...........very carefully!! You don't want to cause a delamination and this can happen with the old glues the early makers used.
The problem is if the rod is fished after this the tip will invariably take the same set.
If you are refinishing just for display this process should be fine.
One method that seems to be better than others is to strip the tip and mount the guides on the opposite flat, then straighten.
If you end up with an upward curve to the tip just fish the rod and it will straighten out on its own.
When you can arrange your affairs to go fishing, forget all the signs, homilies, advice and folklore. JUST GO.