Wheel Walking is a really slick move that isn't as difficult as it looks. The reason why this is because there's always a foot on the tire stabilising the balance. I learnt wheel walking by going along a wall for a while till I my feet got used to what they have to do. The trick to wheel walking is to slow the wheel walk down, its hard to wheel walk fast and takes lots of muscle power to then slow it down and control it. When I started I had the problem that I would keep on speeding up and just go out of control till I found out I wasn't leaning far enough backwards. The second stage I went to was having my back to the wall and simply pushing off straight and wheel walking till I fell off and just kept on doing that. The main advice I can give to wheel walking is lean backwards, you might feel you are leaning far enough back but its the thing I changed which made me learn this trick.