I remember learning to hoop on my legs...oh the bruises!! I am a Hoopnotica Instructor and in my class this is what I tell my students about leg hooping as well as what worked for me! First, there are two ways to do it - two legs and one leg - for me I like two legs and at my upper thigh. With two legs you will have two points to push the hoop - one leg will be your front leg and one the back leg - the front push will push forward and up (keeping that foot on the ball helps) - the pushes happen right after each other. It is like your front leg pushes and your back leg flicks!! When using one leg - that leg needs to do both front and back pushes - keep your foot on the ball and press your heel into the floor - you are going to need to move fast and with some energy. If the hoop is falling below the knee you need to really flick the back leg with using two legs.
I also tell students that if the hoop is falling to let it go and just start again so that you do not damage your knees or bruise your shins.
Just keep trying - it takes time and practice! Have fun!! Happy Hooping
Here is a video tutorial I made for my friend Amy that might help you: