About a year ago, I started using grease-the-groove to go from exactly 0 chin-ups to my current max of 5-6. My schedule is to do GTG 3X/week in a somewhat condensed way: if I'm also lifting that day (modified Starting Strength), I do 6 sets over the course of an hour in between sets, then do another ~3 sets spread out over the rest of the day. If I'm not lifting that day, then I spread out the sets to the extent that my schedule allows. I now do ~3-4 reps/set, totaling about 35-40 reps/day. Once a week, I try for my max on the day's first set.
For the last ~4 months, though, I haven't gotten past my current max. No change in body weight that would explain it. How do I revise my programming? Let's say my goal is to get to an arbitrary 10 strict reps.
Here is a similar question with an excellent answer, but since I am already doing a high volume, I could use concrete guidance about how to implement those (or other) recommendations in terms of exact reps, sets, and days/week.