As I stated in the video I saw a tutorial online how to use candle flame to shape hard plastic tubes. That idea gave me this idea for using the glue gun to shape soft plastic.
Shape hard plastic rods tutorial by Lesley Shepherd here UPDATE Sept 2020: I'll leave this link here but it no longer goes to the original blog post, the post was moved or removed. Please leave a comment if you know where the post was moved to: https://www.thesprucecrafts.com/make-miniature-bottles-from-recycled-plastics-2366823