I worked up to one arm pullups by doing Gtg oa negatives every time I passed the bar, then half oa pull ups, then oa pull ups.
I already had a long history with pull ups, and I dead lift and loaded carry alot, which I think gave me a strong base of support.
But I probably did 8-15x1 each side every day. I had to give up gtg oa pull ups eventually because I couldn't get my lats to relax.
It sounds like your goal is higher rep pull ups? If so, I've heard people say good things about the fighter pull up program, but let's see what others experience has been...