Stop! Fast! Giving yourself a few extra seconds between repetitions should enable you to perform more reps in whatever set-and-rep combinations you’re using. Let’s say you can perform five sets of three to four reps without pausing. If you pause three to five seconds between reps, you might be able to get five sets of four to five reps, thus recruiting more motor units.
Another system I like for pullups, which might work well for someone at your strength level, is to perform 10 sets of the exercise. Take the number of pullups you can perform, which in your case is six, and divide that by two, which is three pullups. For your first workout do 10 sets of three reps. Every workout try to increase the number of reps you can perform until you can do 10 sets of six reps. When you can do that, you should be able to get a dozen reps by yourself.
Negatives are great for increasing pullup strength, especially for beginners, who often cannot perform a single repetition, but you need to continually vary your workouts to ensure continual progress.Charles Poliquin
Another system I like for pullups, which might work well for someone at your strength level, is to perform 10 sets of the exercise. Take the number of pullups you can perform, which in your case is six, and divide that by two, which is three pullups. For your first workout do 10 sets of three reps. Every workout try to increase the number of reps you can perform until you can do 10 sets of six reps. When you can do that, you should be able to get a dozen reps by yourself.
Negatives are great for increasing pullup strength, especially for beginners, who often cannot perform a single repetition, but you need to continually vary your workouts to ensure continual progress.Charles Poliquin