I make model graphicxs. Most don't know this.
Only thing I would use is a bit of light heat from a heat gun.
The florida sun is also helpful. I've removed vinyl lettering from trucks that was years old using just the sun's heat.
There will be some adheasive to remove after the vinyl is removed. I use professional stuff for this. You can buy a product made by the 3M company that is designed to remove the adhesive. Body shop supply places carry 3M products.
Although I have never used this, I'm told lighter fluid works also?
Patients are important.
Let us know how you make out?
Charles