Finally getting around to it, huh?
I would suggest poking around Cosworx for a medium-to-long wig that has bangs and a lot of volume, and maybe layers already in it. You're not going to be able to get the giant poofy look he has (without getting a punk wig and looking kinda silly), so I'd suggest going for a more "natural" version of what his hair would look like in the real work. Tease up the bangs and the layers, maybe cut some extra layers in, and style it so it's big and floofy and curls up at the tips.
And yeah, regular old hair spray will work to style it. You shouldn't need anything too complicated - maybe some hair glue (a spiking glue) if you really intend to go for some super-big spiky bits. Don't think of it as styling hair, think of it as sculpting the shape of Yamcha's hair. It looks scarier than it is.
Here is the problem.
