Hair straightening?

I've Googled but haven't come up with anything useful. About the only thing mentioning his daily hair routine was some interview from way back in the Buffy days where he mentioned "getting out of the shower and putting some texturizing gel in" or something, and now I can't even find that.

Anyway, maybe this is just too obvious for anybody to pay any mind to, but I noticed throughout watching a lot of Buffy and Angel that Mr. Boreanaz's hair seemed to be pretty inconsistent from episode to episode, or even scene to scene. The style was the same (crown up, faux-hawk sometimes), but sometimes it was wavy, sometimes it was a bit curly, sometimes it was spiky, sometimes it was very spiky, sometimes some was spiky and some was wavy/slightly curly, etc. I know in the beginning episodes of Buffy, he had wavy hair and then it progressed to the straight-spiky style most of us recognize.

I'm only curious because I really like the style and I've been trying something similar myself.

Some examples:

http://www.onlyinphiladelphia.com/wp-content/uploads/2010/12/david-bor eanaz-angel-buffy-400a092607.jpg
http://images2.fanpop.com/image/photos/9100000/David-B-angel-9193862-6 30-785.jpg

Cena doesn't overcome any odds. He's a wrestler with a God Mode cheat on.