Spin is a very useful thing in diaboloing. The faster a diabolo spins the more stable it becomes & the more time you will have to perform more tricks. The Chinese whip is a very useful move as it is an impressive way to build up a lot of spin very quickly.
A Chinese whip is where you wrap the string around the diabolo's axle, yank it up in the air then yank it back down again, unwrapping the string on the way down.
Start spinning the diabolo then raise your subordinate handstick up to head height to feed the string into the diabolo on your dominant side. Swing the diabolo underneath your dominant handstick, at the same time circle the dominant handstick over the top of the diabolo then down & underneath it to wrap the string tightly all the way around the axle. As you pull the stick out from underneath the diabolo pull upwards with the wrist & arm to flick the diabolo straight upwards with as much force as you can manage. Immediately after pulling upwards, pull with the dominant handstick diagonally downwards from your dominant side down towards your subordinate side's foot to jerk the diabolo back down again. As it speeds downwards carry your dominant hand back underneath the diabolo to unwrap the string from around the axle.
Your first attempts at this move will all be too slow - this move needs to be done very fast. Make sure you keep your subordinate handstick held at head height throughout, if you let it drop the diabolo may crash into the floor as you pull it back down.
If you need even more speed you can perform multiple whips without unwrapping the string. Instead of pulling diagonally downwards & unwrapping the string after whipping it upwards, just pull straight back down then up again. You can whip the diabolo up & down really fast several times if necessary, picking up lots of spin on the way. This is a move to use in moderation though because...
Too much spin?
Yes, there is such a thing. If the diabolo is spinning too fast during tricks that involve wrapping the string all the way around the axle you will cause a 'ROLL UP'. Chinese whipping will seriously increase the spin of your diabolo. If you keep on whipping you will probably get to a point where you whip the diabolo & it rolls up all of the string into a knot around the axle.
There isn't a great deal you can do about rolling up. You just have to learn when the diabolo is spinning as fast as it can. The amount of speed you can whip the diabolo to depends a lot on the quality of your diabolo string. A tatty length of worn out string that is grey through picking up dust will roll up a diabolo that is spinning much more slowly than a brand new length. Change your string often, also run your fingers down the string to squeeze out any kinks that diaboloing can cause.