I have no trouble remembering words. I used to memorise radio scripts when I was a kid. {Radio Ham etc.} OK bully for me, what's the secret.
A mental journey path works for me. I associate a mental picture with a verse. That picture remains a constant, and I see it every time I sing the song. I can see the shape of the tune as I sing and the pictures attach themselves to the shape in my mind.
The tune shape comes from sight reading music which is essential for a revivalist singer looking for unique material.
This works for me but may not suit everyone {or even anyone} else.
I will lay odds that Dick Miles {above} uses a comparable system. In all the years I have seen him sing I have never seen him lose the words once.