When you want to learn a knuckleball free kick it doesn’t matter what kind of shoes you wear or what kind of ball u use. Everyone can learn it, but the one needs more practise than the other.
Important to know is that there must be no backspin when shooting.
Step 1: run-up; take 4-5 steps back and 1 to the left, then walk straigt to the ball and hit it
Step 2: where to hit the ball? try to hit the ball as low as possible, without giving the ball backspin
Step 3: which part of your foot? between te inside and instep of your shoe
Step 4: body position; it’s important to lean over the ball, that helps to avoid backspin
Now try it step after step and practise a nice knuckleball!