Crude?? The drawings look like they could have come from a textbook.

Using the plastic cup to protect the inner seal surface is a neat trick. I used a similar procedure awhile back to replace the selector shaft seals on a BMW 540i transmission. My "shoehorn" for that installation was a short piece of a jumbo soda straw. Worked like a charm -- After I wrecked a seal trying to install it without a shim.

Nice job.