If you've got a mohawk and need to spike it, check out the method I use. It's hard to find information about this kind of thing, so after lots of trial and error I've started working on this HowTo. I'll be editing it as I find out ways to improve upon it. I also will try to get a video HowTo, as soon as I can find a camera.
KILLER SPIKES: Knox Gelatine and YOU
For huge spikes, Knox has got to be the way to go.
The first time I tried using Knox, I had found a (bad) HowTo online and followed the instructions to the letter. I boiled one and a half cups of water and mixed in two packets of Knox. The directions I got pretty much had me following the recipe on the back of the box. Then they recommended getting a cheap spray bottle, and putting the still-boiling molten mixture in it, so I could spray it into my hair before it got to be lukewarm. The bottle was melting, my scalp was absolutely hating me, and it was just too much hassle that took too long and didn't even work right in the end.
Since then, I've been using trial and error to find out just what makes Knox work as a hair product, and below is my current recipe and method. Enjoy.
For mine (not "huge," per se..) I microwave half a mug of water for about 2 or 3 minutes, then immediately dump 1 packet of Knox in. You have to stir it for a while so it's all liquid. This will be super-hot, and you have to be finished with your hair before it gets super-cold.
I wait for it to get cooled down to the point where if you stick your hand in, it's lukewarm.
Get the first straightened chunk of hair you want to be spiked in one hand, and with the other hand, dip four fingers into the Knox, and generously coat the bottom half of the spike, kind of squishing it all together to get a nice coat going. Then, with your blowdryer on hot and high, dry it thoroughly while standing it up. It's nice to cover the handle of your dryer with a bag or something...
Once it's dry, it should be really stiff, but you still have flexible tips. From here, you keep one hand on the blowdryer, and the other takes little dabs of Knox and just coats the length of the spike slowly, drying as you go slowly up. Repeat a bunch of times and move to the next spike.