I have read of several versions as well, and after trying a couple ways, here is what I did -
One has to compress the rings again so that the fit inside the smaller part of the fork tube bore. One suggested approach is to use a few (sacrificial, because there is likelihood they will get severely kinked) thin feeler gauges (approx .004 - .006 inch) to squeeze the rings inward. However, to insert the damper rod with rings back up from the bottom means that the "step" that is machined on the inner diameter of the fork tube is approximately 2 inches or more up inside the tube, and it this step that is what the rings will catch on and damaged them. To try to get them to compress in that space where you cannot see what is happening with extra long feeler gauges did not seem very likely to work well, and so I decided to tackle the problem from the other (top) end.
Put the piston rings onto the damper rod unit, and also place on your new, red rubber top bushing, but leave the other parts, including drilled circular plate, white plastic washer, etc off. Take your sacrificial feeler gauges and put them on either side of the top of the fork tube and insert them far enough so that they will keep the piston rings compressed until after the rings have gone past the groove for the top round circlip (only about 1 inch or so). Insert the damping rod unit with the red rubber piece in place down into the tube. I did align the rings gaps on the piston rings so that I could easily squeeze them to compress with my fingers and get them inbetween the feeler gauges, and slowly push the damper rod assembly down into the tube from the top. Once it has gone in a little way and the rings are past the top inside circlip groove, you are good!
Then use your socket wrench with extension to push the assembly further down into the fork tube until the bottom threaded end of the damper rod is not quite out - do not push too far because if you push the piston rings past that inside "step", you'll have to carefully draw it the rest of the way out and start all over again!
While the end of the damper rod is still inside the fork tube, I grasp the end of it and give it a few quick rotations of various degrees in both clockwise and counterclockwise directions. I found that this was usually enough to get the ring gaps to move around so that they weren't all lined up together - they weren't perfectly redistributed, but I figure they will do some moving anyway..
So, now you can put the other pieces onto the bottom end of the damper rod from the bottom of the fork tube in their proper order, fitting the retaining circlip on the bottom, and insert the base piece before inserting back into the sliders.
This seemed to work for me and I avoided the challenge of making a ring compressor from a beer can that would do the job inside of the bottom of the fork tube without cutting my fingers.
