One of my coaches showed me a similar exercise using a squat rack. Instead of two people holding the bar, bring the rails on the rack up to about chest-level and load the bar heavy. Then pull yourself under the bar and push it up as you would during the third pull. Lower the rails further and further below chest level to get used to the feeling of getting under the bar at lower heights.
Also, the more the bar rolls along the rails, the more you know you are pulling the bar backwards or forwards rather than just flipping under it.