I am fortunate enough to live alone so i have tried all sorts of DIY solo ideas. Lots of fun ideas here.

For CBT:

Rolling a pool ball down a pvc pipe
Slamming my balls between two dictionaries.
I used to own a boat (big mistake). Once on an early sunday fishing trip by myself i tied my balls to the boat and jumped in (also a mistake). Didnt really work. The water makes everything weightless. I am sure i could have figure it out some how if i put more effort into it. But once was enough to scratch that itch.
Best idea by far is taking 5lb aerobic weights. Standing on a chair holding them head high and dropping. One end of the rope tied to the weight the other to the balls. There is the 1-2 seconds of oh shit😅.

Ive done some self bondage with hand cuff keys in frozen ice. Got to be careful here and give yourself an out. Practice a lot before going all the way. make sure circulation is good. Making sure you have a glass of water near by in case something goes wrong and you are stuck there for a while.

I havent done any of the above things in a long time. My interest have shifted a little more to mental domination and I have been having a lot of fun with DIY chastity and ive figured out a great way to ruin my orgams.

Some risk here no doubt. If we had a trusted partner who could check on our safety after a certain time that would be ideal. But i dont and probably most of us dont.

Better yet just pay for a session. Its always better with a Domme😅.