Having attempted to do the same with Premier Cycles protective film, I have to say that plenty of soapy water and a plastic squeege combined with warm weather or heat is the best method.
I purchased an entire setup of the Premier Cycles precut protective film for cowling, tank, and luggage last year. The only precut pieces that came close to a proper fit were the luggage. The tank pieces were a little off and all the cowling pieces did not even come close, even if trimmed.
In follow-on discussions with Premier Cycle they stated I had the correct pieces and to just keep working the fit with heat and they would eventually fit. After a weekend of effort, I gave up and threw the stuff away. I have installed protective film on almost every bike I've owned and several cars, never encountering this type of difficulty.
I have had good luck with their luggage racks but cannot recommend their protective film.