Both my parents did this, but I don’t know what the process was then. They died in 1997 and 2001, aged nearly 90 and 94. In the end when they died my mother was not accepted, but my father was. I don’t know why. It was such a relief not having to have a funeral for my father. He certainly didn’t want one. Now, of course I know that theres’s no need to have a funeral anyway, but we didn’t know then, and my mother’s was a bit farcical, since she had outlived all of her friends and most of her relations, and certainly had no religious faith.
When my father was accepted, I don’t remember it being at all complicated. We had a lovely family lunch in celebration of his long life, and it was all so much less traumatic than when my mother died.
I would urge anyone to do this. If you can be useful after your death, why not be?