I have been working on getting a better Muraiki this week and Chikuzen had some great tips for me on this topic.  The way he had described it to me to make my technique better was to keep the cheeks pulled in and raise the back of the tongue up so that the air was channeled down the center of the mouth in a powerful stream that makes the air almost sound like a whistle when leaving the embouchure but not quite.  If the note jumps to kan then back off on the pressure just slightly.  This worked well for me.  Your mileage may vary.