Another method that doesn't work is to fill a bottle with oil to the required level, then carefully plunge the tip of a meta rod heated to red heat, the neck should break off. Only it doesn't.

I used sunflower oil when I tried it, thinking about it now perhaps I should have used engine oil.

The bottleneck I use now is the nozzle from a welding torch I find the extra weight gives excellent tremolo.

Regards

Chris