I'm thinking IQ set at 1-5 will have signature attacks and defenses worth double while 6-10 would have triple. The Flash is a forensic scientist so he's got a lot of brains, a high IQ would give him a slight boost to stand shoulder to shoulder with Superman and Batman. Speaking of Batman, it'd make whatever his signature move is a beast. If his strength and IQ are high you're looking at a signature move worth 6 hp. 

~KL~