When it comes to window rubber, I'd take new Brazilian rubber over German NOS any day. I put an NOS American style window rubber on my 63's windshield . . . it shrunk and cracked in the corners within 6 months. I've got cheap Brazilian Cal-Look rubber on my 74 Super that still looks great after almost 9 years.
I'm not sure I understand exactly what step you're having trouble with, but . . .
When you are trying to put the seal on the glass, do not use ANY lubrication of any type . . . it doesn't make it go on any easier, but makes it easier for it to pop back off. Make sure the rubber is warm. The warmer the better . . . to a point anyway. Laying out on asphalt for a little while on a sunny day will do the trick. If your REALLY careful about how long you "cook" it, a microwave will work. Really, it will. Been there, done that. Just don't overcook it. And don't put the trim in the microwave. Just the rubber.
Once the rubber is on the glass, put the trim in it. Then install it in the car. I have done a whole lot of Cal-Look window rubber, but only the one American style. Cal-Look is definilty easier. If it's getting the trim in the rubber that you having trouble with, make sure your trim and rubber match . . . the older American style rubber used a metal trim that had a "C" shaped cross section. The rubber had more or less just a slit for the trim. The newer American style rubber used a chromed plastic trim that had kind of an inverted "T" profile that went down in the rubber. If you've got the old style rubber, you'll probably never get the plastic style trim into the grove.
For installing the window back into the car, I have found that a large gauge Weed Eater cord works great. So does 12 or 14 gauge automotive wire. Both are relitively thin, but don't "bite" into the rubber. Wrap the cord around the groove where the lip of the body goes. When you install the glass into the car you need to use some lubrication. Most people say use soappy water. Some use petroleum jelly. I've heard of people using WD-40 . . . or lots of other lubricants. Now, don't laugh . . . I use K-Y Jelly. Just a little on the sealing lips of the seal, and a little on the back of the seal (the part that you pull over the lip of the body with the cord. Wrap the cord through the groove all the way way around the glass and overlap it on the bottom so that one of the cord is hanging out in one bottom corner, it wraps all the way around and the other end hangs out the other lower corner. Center the glass in the opening. Push (gently) the glass into the body. Start in one bottom corner, go across the bottom pulling the cord out while someone is, again, genltly, pushing on the glass in the area where the cord is coming out. When you start up one side, stop pulling that end of the cord and get the other end . . . pull it out back across the bottom . . . work a few inches on one side then the same amount on the other. When you get the cord pulled all the way out, the glass should be in place.
OK, now that you are totally confused . . .
David was right (as usual) . . . this really is something that's a little hard to show how to through the forum. We need to have "Tech Session" one day and install some glass. Everyone does it a little different. If we were all in one place at one time doing this "hands on" I'm sure we could all learn a trick or two.
