Replying to Learning off-axis spins... how?

What is the best way to learn off-axis spins and other flips, specifically bio, misty, and flat? My friends have always learned by huck-and-tuck, and hope they can find their footing on the landing, but they either hurt themselves trying or if they do get it, it's kind of out of control. For example, one of my friends learned to do a flat 5 that way, but then as soon as he tried throwing a mute in, it changed his spin and he dislocated his shoulder. What is the best way to learn these spins?