Stay VERY tight and pull up as if you're head is attached to a string and being pulled up to the ceiling. The tighter you are the lighter you are. Lock those knees and squeeze your bottom as if holding a dollar bill there.
No matter what you try to teach a flyer the only way to make a good flyer is to make sure they have no fear. Fear is the #1 problem that will keep a flyer down. A fearless flyer is the best flyer... but after the fear is gone staying tight keeping your head up and just trust your bases and backspots..
Honestly, they need to have strong legs, so have them practice doing a chair sit against a wall for 3 minutes starting and increase it 30 seconds a day every day till they hit 4.5 minutes. Also, once they get up, tell them to clinch their (bottom) cheeks as if there was a hundred dollar bill back there. Always worked for my daughter!