Have access to a Gravitron (pullup

I have access to a Gravitron machine at the gym I am going to.

I can do a few chins unassisted and no pullups.

what protocol should I do on the Gravitron to help increase my pullup count?

10 assisted pullups, rest for a minute, then keep repeating that till failure? Do that 4 times a week?

You have a fully equipped gym then!

I love the Gravitron. Try spit and catch it back in your mouth 5x5 unassisted.

http://en.wikipedia.org/wiki/Image:Gravitron1.jpg
http://en.wikipedia.org/wiki/Image:Gravitron2.jpg

any Crossfitters here with Gravitron experience?

hypothetically if your goal is to do 4- 5 pullups then that should be your rep range