I installed the windshield in my 1962 TR4 several months ago, which I believe it has the same frame as a TR5/250.
The frame was not in the car since I am in the process of completing a ground up restoration on the car. I completed it myself without any assistance, but an extra pair of hands would have helped.
My car has the early aluminum bead trim and everything I read about install the windshield prior to starting the task said to install the rubber around the glass, then install the aluminum bead trim, and finally install the entire assembly in the frame. This process could be different if you have the plastic chrome trim. By installing the bead prior to installing the windshield into the frame allowed me to flex the outer edge of the rubber back to install the beading. With the aluminum style beading I have no idea how I would have installed it after installing the windshield.
I used dishwashing liquid and the rope method. The rope I used was actually what is called 5050 parachute cord . I used the 5050 cord since it is only slightly larger then 1/8 inch in diameter, has a very smooth outside covering, and has 10,000 pound pull strength so there as no way I was going to break it and the small diameter of the cord made it easier to pull the assembly into the frame.
You can buy 100 feet of the "5050 parachute cord" on ebay for $7.95 plus shipping. I have found a lot of other uses for this stuff over the years.
I can see how you could damage the rubber if you were using rope with a rougher outside surface.
It took a bit of work to get the last side in by myself, but the end results look great.
Visit my new and improved personal website at:
https://jakegingervila.wix.com/bobs-vintage-cars-
Vila
1933 Chevrolet
1962 Triumph TR4
1984 BMW 633 CSi