I may not be qualified to answer this since I am a newbie, but let me add my 2 cents anyway
I have been practicing pull offs for the last 2 weeks. What I have leanred about them is just like what Pavel said - It's not so much about the strength.
It's more about the feel/motion, if that makes sense. Imagine you are doing a pulloff. The string is already "fretted" because you are applying pressure with the finger. From there let the finger slide off. You will feel that the pressure from fretting the string creates a "grab" between the string and your finger (almost like a speedbump) so when you slide the finger off you don't need to use much strength or motion to get a strong sound. The motion for me is actually very minor, but I get a nice strong sound because of the "grab".
I hope I explained that clearly enough to help you. Like I said, I'm a newbie so maybe I am not wording things properly or maybe my view of the technique is different than how most see it.
Good luck with the pull offs.
You are at GuitarMasterClass.net
Don't miss today's
free lick. Plus all our lessons are packed with
free content!