Basically, it amounts to: once we make contact, I keep the contact.
So you strike with your right and I block with my left, but I don't retract the block. I keep contact with your arm moving long or short as you move your arm. Same thing with the other arm. I maintain contact and therefore control what you can or cannot do. It isn't strength on strength, it is redirection of force and keeping enough pressure to make you use energy.
If you try to make it strength on strength, you will lose. You can also trade off hands that keep the contact as you go.
Falling leaves is a good example of this. Lets say you strike at me with a right. I block downward with my right hand, and then my left and back to my right in a circular motion. moving up your arm (typically: right, left, strike to you head, face or other target)
This has the effect of keeping you off balance and focused on your right. You should be moving on a 45 to the oponnents right side as you move closer into him. (your left) The momentum of your movement should be used in conjunction with the strike.
Now, as far as sparring goes, you just keep contact, moving long or short in response to your sparring partner. It's pretty funny against someone who has not seen this before.
Wing Tsung guys actually do a verision of this in transitioning between tan sau, fook sau and bong sau, though they don't refer to it as such. But the idea is the same: once contact is made, it is kept until you strike or the opponent breaks it off.
Practice of this is really good for developing fluid movements and transitions, as well as developing a feel for what your opponent is going to do (without resorting to having to put your hand or arm in a specific place in order to tell what they will do.)
If you can develop a good rolling jing, it will serve you other places too.
(jing is just a way of movement or energy - each of us has a natural jing that suits us. because we are all built slightly differently, our postures and movements will not be exactly the same. Likewise, our personalities will also influence what jings we choose when adopting a fight style or system. I guarantee that my tiger or kuntao does not look exactly like anyone else's. Good instructors understand this.)