I did sets of 'Australian chin ups' when I started. I was a fat bastard back then and couldn't do a normal one either. I switched to regular chins pretty quickly.
Julian demonstrates Australian Pull up - YouTube
I would do something more structured than 'everytime I walk past the bar'. Do maybe 3 sets of aussie pull ups then say 3 jump ups / eccentrics once every 2-3 days.
I can do around 15 chin ups at the moment and 1 single with 50kg attached, working towards 1 hander..... you will get there, but it sure is a tough exercise.