Sorry that there is no an exact annealing temperature, duration and cooling rate.
Different hot air gun has different heating efficiency. We set in about middle hot range of the hot air gun, about 300C for OD12mm crystal tube. The distance between the tube and gun is about 60mm. While heating, turn the tube again and again until the tube softens. And then turn the angle you want. You can use a wet towel to cover the tube and cooling it in about 15 seconds. In final, pull out the silicone strip from the OD12mm acrylic tube.