ok Yue. well if its a technique your looking for, I got one for this. Its a variation of Single whip used in Chen style.
Normally you do single whip with your body to the side, it a 30% 70% wieght distributed posture with your body in a T shape to thiers, for lack of a better reference to help you understand. in the Yang style your body is ussually the " l " part of the T. In Chen, in this movement, your gonna be the " -- " part of the T.
How the movement goes, you stand in a Mountain climbing stance, when he starts the kicks, your front arm will make the crane beak and move down like in snake creeps down. The hook should be facing upwards with your arm turned to creat a hook with your beak. wrap it around the first leg to trap it. He will naturally try to show off, by kicing with the other leg, bring the other one around and grab that one. If you can block a kick you can grab it. Then hes in a very very bad position and you can do what you want. A leg/ankle lock with one of the legs, kick to the groin, if you lift him up you can do a kick to the lower back, whatever. Hes completely passive.
If that one doesnt work for you and his kicks are too fast, or hes too phycally strong to grab his feet, too heavy to lift, or whatever, lets say he approaches you with a kick from his left leg, sidestep left and toe kick the leg into his right. try to get at the base on the back of the calf on the back of the leg if possible, or 4 body inches (finger widths) above the knee on the outside of the thigh, either will make that leg numb. meaning he cant do the crab walk anymore
Its just temporary too, so after a few minutes, hell recover. If you cant find one of those targets the left leg should hit the right and destroy his root, making him fall or loose balance anyway.