heat gun
I have used a wagner heat gun for over twelve years. The technique has become second nature. A combination of rotating of the bottle and distance from heat source is key. To avoid the foil on the top from sticking up after heating, i use my palm to hit the top of the bottle after each heating. I am used to it but it can be quite hot to some people, so use a cotton glove or even paper towel. Short of an expensive heat tunnel, this is quite affective.