We looked into making our own 8” mirror so the kids could see Halley’s Comet back in 1986. The basic grinding process was simple. As you got closer to the final surface shape, you had to wet the surface to make it reflective, then look at a sheet of graph paper placed several feet away.
Any mirror distortion was evident in the reflected image.
Once the reflected image was correct, you had to send the mirror off to have it coated.
We ended up buying an 8” silvered mirror and constricting the rest of the telescope.
http://www.scopemaking.net/mirror/mirror.htm
My best friend was part owner of a ship repair company with 4 other guys, one of them was into telescopes. They would grind their mirror, not sure of the size, at their meetings pushing and pulling back and forth. Took them awhile.
They used a sonotube?, one of those molds for pouring concrete pilings, as the body and built a Dobsonian? telescope that was very large. You had to stand on a stepladder to see into this thing.
I’ll never forget seeing the Orion Nebula through it. It looked just like the pictures in astronomy class I was taking at the time. I was amazed at the quality of the images, especally as it was a DIY project.