First, easy step: placing the rubber seal around the edge of the glass. I have the glass sitting on top of a piece of sponge packing material - this avoids the seal slipping off as the glass is moved around. No lubrication used for this step.
After fitting the seal, I inserted a length of thin rope in the seal, all the way around, and taped the rope ends to the inside of the glass.
Then I offered up the seal+glass to the window opening, and after lining it up, just let it rest there. Getting inside the car, I had a young helper push gently on the outside of the glass, at the bottom middle, where the rope ends emerged on the other side of the glass. Detaching the tape, I pulled on one of the rope ends (gently, pulling towards the centre of the windshield) - this pulled up the edge of the seal as the rope came out, and the edge would then fall down on the near (car interior) side of the lip. This process was continued, with the helper pushing on the glass, and me pulling on the rope, until the rubber seal was over the lip all around.
Here is the situation at this point:
Next, the hard part: putting in the lockstrip, which looks like this.
The lockstrip is a fairly rigid piece of chromed plastic, and needs to be inserted in the groove around the rubber seal on the outside of the car. Here are the tools I used:
There is a container of dish detergent diluted 50:50 with water, used as a lubricant, a brush for painting the lubricant on the seal, a small nail-lifter used for teasing seal edges over the lockstrip (and used with extreme caution!), and the absolutely essential custom lockstrip tool without which the job would be almost impossible.
In the above photo, the lockstrip is seen threaded through the tool's head, which is shaped so that it spreads the seal's lips apart. As the tool is moved along the groove, the lockstrip is threaded into position and the seal's lips fall on top of the lockstrip, so securing it. The more lubrication used, the better.
At least, that's the theory. In practice it's quite hard to make this work well in the corners of the windshield, where the tool is being turned through an angle, and the seal tends to twist out of the correct orientation. If one edge of the lockstrip gets properly covered by the seal, then the other edge can be prised over it by careful use of the nail-lifter tool. I had to do this at each of the four corners, and it was quite time consuming. (On the MGB windshield I remember the locking strip was rubber, so much easier to manipulate.)
Finally, after going around the whole windshield, the locking strip is in place:
I will leave it untrimmed to the correct length until it has settled for a few days in the sun. Then it will be a matter of cutting it, inserting the end into the seal, and covering the join with a small piece of chrome trim for the purpose, which I have on hand (in the plastic bag shown above).
The cat appears to think the job is satisfactory: