Extended breathing can be practiced in almost every situation. When you breathe out, remain in the exhalation spirit a while after no more air comes, and when you breathe in, keep the inhaling spirit a while after you have filled your lungs.
The best is if you do it with belly breathing, but that's not completely necessary.
You can use this extended breathing together with things you do. Breathe in when you pull something, breathe out when you push - for example doors. That's fun.