I had good results by using some of Stew Smith's workouts. I've never seen the Armstrong program, but it seems to have a lot of the same principles, such as using max sets, changing the grip on different sets, and using the pyramid.
IMO, you may not want to do some of those workouts every day, especially if you are just starting. However, listen to your own body. If you can do it, go on ahead. If you need a rest, then pull back a bit. Sometimes taking the day off is much better for you than working out.
Also, it takes time to improve pullups, so don't get discouraged. I swear, one day you will just magically find that you can do more. It's not like pushups or situps where you have light resistance; pullups are a full bodyweight exercise. It's more like trying to improve your reps on benchpress with your bodyweight on it.