Chi Sau or sticking hands is taught in several stages, with initial moves being taught at the Siu Nim Tau level, the Daan Chi Sau or single sticking hands is first taught, elbow positioning, stance training and basic feel of intention is learned here, with the three (3) primary elements of Bong Sau, Taan Sau and Fook Sau being trained in a dynamic way.
Finally the two (2) hands are placed together to form the Seung Chi Sau or double sticking hands, at this point in time the Poon Sau or rolling hands is trained, until the student can instinctively use the forward springy forward force of Lat Sau Jik Jung.
Once this is understood, the student then commences with some basic attacks and defences until nothing is planned and users are instinctively reacting to each other's movements and positions, relying only on the feeling generated upon the forearms.
At an advanced level, Chi Sau can be performed with a blind fold, where any situation can be simulated to such a degree that each person are countering each other's attacks and defences.
Chi Sau can be thought of as where anything that obstructs or blocks our hands can be instinctively countered and is the corner stone of the system and the drill that differentiates Ving Tsun from any other form of martiial art.The idea is not to endlessly block your opponents hands, but to attack your opponent.
If you are not countering your opponents attack with an attack then it is not Ving Tsun Gung Fu.