are you trying to do a fan mohawk, or a liberty spike mohawk?
if its a fan hawk, i really cant help you, lol i hate the "fan" hawk, i have a 12 inch hawk so its extreamly hard to do a fan hawk...... but i always do a liberty spike hawk, witch i can get perfectly, lol... im putting a video on the site soon within a few hours, so look at that, and i hope it helps
My advice is add product slowly, especially if your using just hairspray. Spray your hair and comb through and blow until it can stand on its own. Then use a hair straightener on the lowest heat that will get the job done but not fry your hair. The straightener will help form it and shape it and then just add a bit more spray, blow dry it, straighten. Repeat this until its as solid as you want. I started using just hairspray and it can still get really stiff but remain durable.
If you use a straightener make sure you don't have the heat too high for your hair, or give it too much at a time because it will fry your hair and it will break off. I made that mistake in the learning stages of this and I am now waiting (im)patiently for my hair to grow back to spiking length