I'm one of the types of martial artists that a lot of people make fun of... the type that's been obessed with the arts my whole life... and while primarily I study and teach Shaolin Kung Fu I also have taken and teach Karate, Wing Chun, Kenpo, Thai Boxing, Savate, Ba Gua, Tsing Yi, Systema, Capoeira, Ninjutsu and Jiu Jutsu. (And, in case you're wondering... no, I have no life. Ha)
When someone is a whirlwind fighter, meaning they're flailing around wildly and probably don't care much about pain you may inflict or even if their injured, I've found that attacking their head or torso is usually not a good idea. Whirlwind fighters will punch, kick, claw, bite, or tear whatever they can, and trying to grapple with them is usually the WORST idea.
However, it's been my observation that westerners (who grow up equating fighting to boxing) rarely think about using their legs, and even more importantly, rarely think about DEFENDING their legs. It's becoming a little more common now to do so, because of UFC and MMA, but it's not often that whirlwind fighters think along those lines.
So, my advice is to attack their legs with whatever kicks you're most comfortable with. A hard, straight kick to a point about two inches above or below their knees will break or hyper-extend their knee. If you're more comfortable throwing round kicks, a fast stinging kick to the inside of their thighs is often an attention-getter, which may cause them to pause long enough for you to perform a fight-ending technique to the head or torso.
I wouldn't try sweeping them for two reasons. One, if they're in a state that they don't care about injury, they'll continue fighting even on the ground, only now their legs are free to kick wildly as well. Two, if you happen to miss or take too long to make it work, your back or sides are wide open to whatever sadistic punishments they're trying to dish out.
I realize I rambled a bit, but I hope this helps.