Hey mus,
You pretty much describe the pull-off process. But like "everything" guitar, it takes practice to get the technique.
When you pull-off, give it some "umph" power. Let the string know you just pulled it off. ( no remarks from the peanut gallery..
Try this. From an open G string, place your index finger on the second fret, the "A" note, and "pull" off. Your finger tip literally pulls at the string. The more force you use in pulling your finger off the string the more tone you get.
But keep in mind, hammer-ons and pull-offs are subtle nuances in your playing. They add a little frill to the melody. They are not meant to be "power notes". Just a little lace around the silk.
**
LC