Aww, Ernie that is great!
Good info so far. There are some stickies in this section as well.
Good nerves have to be there. Trust in the handler is huge - they will look to you to pull the hand out of the fur, the face out of their face, etc. Set them up now to know that you have their back and they will relax and enjoy.
I have not done therapy with my GSDs, but did with a BC-Chow type mix who did not like it after all! That was exhausting for me - I had to do the therapy visits until I saw she just was not into other people. I also had a GSD-Schipperke who did it for a number of years and then he also had enough, got more "Schipperke" and as he matured into a full adult, became more watchful, less welcoming. Also to be noted - he was extremely sensitive to the environments in which we visited and the pain/upset we encountered so I had to be sure to only visit facilities where there was a positive at some point (no hospice, no only difficult cases).
I had him from 6 months on and used a lot of food to create positive associations with things - wheelchairs, walkers, canes, crutches - if he saw them he was treated. To the point if he saw a baby carriage, he would start to chase after it - treat! I get a treat! Good thing he was small.
He had a natural infinity for people with developmental disabilities and very sick children. So there was nothing to teach him there.
I also taught a say hello command, which helps tons. Then, always work on cute tricks, which helps people who don't want to or cannot pet a dog - they can sit and watch twirl, spin, crawl, etc. and enjoy that.
It is very rewarding, if your dog likes it.
And if they don't, it's very tiring!