How long did you train before you were able to do those 36?
You’ve been on a rep progression all this time, right? Try different progressions like weight progressions. Get a dip belt and put a 25 pound plate. If you don’t have a dip belt, get a backpack and put the plate in it.
If you don’t have plates or don’t want to go heavy, you can try rest-pause training. After your 36th rep, rest for a few seconds (maybe 15 seconds) and continue your set. Do this around 2-4 times in your set and make sure that on each workout day, you reduce the pause times (from 15, you make it 12), or you increase your reps after each pause.
Also try slow negatives. After exploding to the top, lower yourself for about 10-15 seconds. Do this each rep.
And if you can do 36 pullups, I’m sure you can do 1-hand pullups. Do as many as you can alternating style. Pullup with your right as much as you can then do it with your left as much as you can, and without rest, go right back to your right, then left, and so on until you can’t complete a rep without rest anymore.
The key here is to provide your muscles with different stimuli so that you will be able to shock them into new stages of development. You can invent ways to make your pullups different, and that would do the job.