Glad you had success with this!
White Spirit is the perfect glue remover.. just dissolves it away.. then once dry, its glue again.
It is the only way i remove Mylar and even the most fragile of artwork can have mylar removed relatively safely.
If the paint has less grip than your mylar then the paint will come off.. simple law. Negate the glue on Mylar and paint is left behind.
if you could get White spirit under the whole section of Mylar at one time then the whole lot would just slide off like a water decal.

Cheers PG!!