Take some marshmallows (mini/jumbo/standard, whatever you can handle) and stick 'em up your bum. then diaper up and hold on tight. the sugar in the colon pulls water in, which then saturates any poop and brings it all down the line for expulsion. usually takes 5-10 minutes to cramp. I've had uncontrolled messing within 15 minutes. and I mean UNCONTROLLED...
lock the bathroom, and put the key in a block of ice. at some point, do the marshmallow trick to get a nice mess in before bed. then change, and go to bed in a fresh diaper. day two: wear until the key block is melted. size of the ice block can be up to you
Closest I've come is wetting, messing after a marshmallow enema combo, then 'finishing' by rubbing against the floor. The whole experience was so exhausting, I just stayed on the floor in my onesie and paci, and just passed out.