You have absolutely come to the right place!
I’ve had a good look around and unfortunately I haven’t found anything about self checking for testicular cancer that is specifically aimed at someone with a learning disability, but there are some easy-to-understand guides out there that might help you understand the process and be able to successfully explain to your son.
If you haven’t already, have a look at the information provided by:
Movember explains it simply, and uses quite a relaxed, tongue-in-cheek tone which could be helpful.
I hope this helps, interesting to see that it’s so difficult to find this crucial information designed to be easy to understand for someone with a learning disability. I’ll pass it on to the relevant team at Mencap to see if there is anything we can do.
All the best,