I been rehabbing a pulley injury on my middle finger A2 and A1.
I was recommended single finger density pulls using a homemade 18mm plywood edge attached to a theraband.
I decided to try this out on both middle fingers as I knew that the other one was dicky too. The protocol was 10secs on minute off, 5 sets twice a week. Pulling as much as is slightly uncomfortable.
I was so impressed with the results that I programmed my hangboard app so I could do all 4 fingers on both hands. This results in a 12 minute session, twice a week.
The initial session revealed several interesting things; I couldn't get my pinkie's into half crimp, my left ring finger was dangerously weak, and even accounting for the difference between drag and half crimp, my left pinkie was one of the strongest on the hand. It was obviously compensating for the ring finger.
All very interesting, and I think I'll keep going as part of general conditioning.
As a side note, the A1 was particularly slow to recover, and I found building a hand jam box and doing weighted lifts with it really helpful. I plan to get back on my jamming projects in February.