To learn how to create the reverse footlock I used a tutorial I found on the internet by Javier ' Goosh' Solsona. I found the tutorial to be very straight forward and effective as I only needed to go through it twice to pick up the method. The link is here : REVERSE FOOTLOCK LINK
He also has a bunch of other tutorials up on how to create elastic feet, FK/IK switching. I have skimmed through a few and may use a few more in the future to learn a few things.