did a (shitty) one arm pullup a few years ago with a similar idiotic deadline.
doing variations is generally a good idea, although I find there are too many wobbly chins/pulls in the vid above.
mastering them is even better - you need to understand them and above all else, understand how to pull with your lats. The guy in the above video, with the yellow shirt, does it well.
With standard PUs, pull as deep (about sternum) as possible until form breaks down.
Identify weaknesses early : grip, arm-flexors, abs etc.
Build them up a bit if they are severly lacking, ie isolate them.
FOr grip, the easiest way is to hold yourself with only one arm and go for time. Multiple sets and a bit o' extra weight should suffice.
However, if it's the arms that are weak, don't overshoot. Your ellbow will take a major beating from all the chinning already. I'd even go so far and say if your arms are already decent and you do bodybuilding type "arm-day" workouts, drop them until you achieve your goal.
Sacrifice armdays on the altar of OACU and he might show mercy to your ellbow joints.
Implement heavy chins/pulls exercises asap.
I cannot stress this enough.
This 30 rep rule sound about right, but repping out is way different then actually doing heavy one arm stuff.
Do heavy bilateral doubles and isometric one arm holds at the top, where you progressivly play/cheat with ROM.
This two exercises alone can take you there.
Bodyweight is a BIG factor.
If you're 220+ heavy dude and have never done solid chinups/pullups with your lats, this might be a foolish undertaking.
If you're plain fat, gtfo and enroll yourself in an eating contest or in hundred slices of cheap bacon.
This one's not for you, fattie.