remember to "Smell your breath" (Sniff as you use mouth pressure to blow)
If that does not work I can suggest hallucinogenic mushrooms and play all night and you will circular breath.
One night every one in the room leaned to circular breath while on shrooms.
4 guys! What a trip!
Also you want to keep a full lung of air pretty much at all times, you cant circular breath with an empty lung very well. Take tiny gulps of air into your nose and eventually you will figure out that your mouth is able to push air out your lips with cheek muscles.
kthanksbye.