A good and quick way of inducing a quick bowel movement when you're unable to poop normally is to use an enema which you can purchase at most pharmacies or other health stores.
The enema will force warm soapy water up your anus and you'll be pooping very quickly after that so be near a toilet or have a diaper on after you do the enema because you won't be able to hold it back.
You can also drink cranberry juice or eat cranberries which can help you go poop when you're constipated.