my lo has always had trouble poo'ing. we do cycling motion with his legs, push his knees up against his tummy and rock him back and forth / side to side, and rub his tummy in a clockwise circle from the bottom of rib round down to the smile crease, and scoop downwards from his ribs to the smille crease, like you're scooping sand... if that makes sense!
hope you find something that works!