Drip Rail Molding Install

[DAZSTANG]

I have made two attempts at $50.00 an attempt to get aftermarket Drip Rail Molding installed on my 1966 Coupe.
I purchased the Drip Rail molding from C.J. Pony Parts and I find their product line to be acceptable. CJ's service department spent some time with me assisting in the installation process. However, I am finding that there is not a lot of consistency in the manufacture of this item. The manufacturer of the item is CORVEX.

After my first attempt at twisting pushing, grunting and hitting with a rubber mallet, I was unable to get the molding to fit and eventually scratched and caused damage to the new finish.
I made the assumption that my car may have to many layers of primer and paint. So I sanded the surface to bare metal brushed on primer and re-sanded to smooth.
The second set of Drip Rail came in (Corvex)and the item was even tighter that before, not allowing it to snap over the drip rail edge.
Does anyone have suggestions as to manufacturer, supplier or method of modifying the drip rail so that it will fit?