It is literally not possible. If you maintain neutral buoyancy, you will not ascend. You will stay at your current depth. If you are neutrally buoyant, you must do something to begin your ascent. The obvious thing to do is give a light kick to start going upward. As soon as you do that, you will become positively buoyant, and when you feel you are positively buoyant enough that your buoyancy is bringing you to the surface, you must vent air to maintain control. You should be close to neutrally buoyant throughout the ascent, but you are actually going back and forth between negative and positive.
Some instructors (and report area divemasters) go so far as to tell students and divers to dump ALL air from their BCD before they ascend. That will work for divers with thin wetsuits and reasonably good weighting, but it is a bad habit because in cases where diers have extra weight, as with a thick wetsuit, they will become too negative and will sink.
(I have an article on this pending publication through PADI in the next year or so.)