Recently I have installed both the front and rear trim strips on my 67 2+2. Here are a couple of observations. First, don’t rule out that your windshield gasket is flawed. 10 years ago, on the same car, the wife and I struggled for hours to get the front windshield glass installed. It turned out the gasket was not quite right for the opening. Close but not close enough. I eventually purchased a new gasket from a different vendor and the glass installed relatively easily. My current gaskets were purchased from SNG and I’ve been happy with them.
The same is true with the trim pieces. Again, it is always possible that your particular trim piece is not formed quite correctly. It doesn’t take much to screw things up. Because of the C shape, they do not respond well to hand tweaking.
I may not be of the school that says lubrication is required. The problem is the only thing that holds the trim piece in is the friction of the rubber on the trim. Or at least that is how I think it should work. On my upper trim piece on the rear hatch glass, while test fitting I was convinced it would never fit. I ulitmately started from one end, working it into both gaps and holding it in position with duct tape. After I got it generally fitted, I came back to the middle and gradually working my way outward applying small drips of Super Glue to the adhere the rubber to the trim. In some cases, the trim still wants to pop out as soon as the duct tape is removed. I was able to apply the Super Glue and push the trim back into its correct position. Fortunately the SG bonds within seconds. When I was done, the entire trim strip was held into position by the SG. Some SG did make its way onto the surface of the trim. I was able to use a razor blade to scape the trim clean. If it gets on the rubber, you can’t really scrape it so be as careful as you can. Literally one drop is all you need. More is not better. And I’m not sure how the SG would have adhered if lubricant had been present.
If you really want to be depressed, watch the factory assembly line video posted recently here. There is a short clip in the video where they installed a front windshield. In about 10 seconds! Unfortunately there are no shots of the trim installation but at the pace that assembly line moved, you can be sure they didn’t fool around with Super Glue, etc. After all the trouble I have had with glass and trim, I am amazed that the process worked at an assembly line pace.