I just rested my weight on top of the cart and used my good leg to push it around like a scooter.  The biggest problem I had was picking up anything heavy.  Employees or nearby shitlords were always offering to help me when then saw me awkwardly moving a huge bag of dog food or a case of water.  (I do the same thing when I see someone old or injured.)  Big surprise, not a single fatty ever offered to help.