I am a professional installer. This is a very good tutorial, however, I would not use baby shampoo, it can leave a residue (despite what the video says).
The only thing I will say is that it takes a fair amount of practise to get good at this, and if you're using an expensive film, you can easil...
Gavin Rapp should stick to loading things onto the FEDEX truck, film making is a little out of his abilities.