For ease of calculation let's say you maxed out on 8 repetitions, when greasing the groove you will be performing 50% of your max reps, in this case 4 reps per set between 5 and 8 times per day with a minimum of an hour of rest between sets.
Do this daily for 3 - 4 weeks before re-testing your max reps, provided you followed the program to a tee you'll likely be smashing out 10 reps per set after greasing the groove for just under a month.
Greasing The Groove Quickly Adds Up...
Think about it, you may have previously been performing 3 sets of your max reps when performing your back workout once a week.
That's a total of 24 pull-ups a week.
Enter greasing the groove.
You're now performing 4 reps per set between 5 and 8 times per day...
That's 32 pull-ups a day.
That's 224 pull-ups a week.
Run this program for a month and you've performed 896 pull-ups instead of your usual 96 pull-ups.
With the large number of rest between sets you'll find you've increased your volume ten-fold yet you likely won't feel any additional fatigue from doing so.
That's the power of low rep, high volume training with large rest periods.
After a month re-test your maximum and if you wish to continue greasing the groove for that particular movement base your 50% off of your new max and continue...