Method 1: Shrink to the sides with the windows in, keeping it clean with glue.
Method 2: Cutting the film long, tack it down in the middle of the bend and then pull shrink the sides. Try using a jig or clamps in order to keep the window still
Method 3: Some corner windows on the old Chevys are so fickle that sometimes getting them factory smoked is an easier alternative. It should cost around $50 for a 20% smoke job.