Serious guitar cleaning

Like I said on the other thread I just started, we had a fire at our practice space. We rescued our guitars, took them to the local guitar wizard, who estimated that it would cost me at least $240 to have my guitar cleaned and a crack in the neck looked at. This guitar cost me $300 when I bought it, so I said fuck it and brought it home.
My plan is to do the best I can to clean it myself and just have it at home for messing around or home recording. It's not a fancy guitar but it's been my main guitar for 6 years and I like the way it feels.
So basically what I have is a guitar covered in grime and ash. I need to know the best way to clean it up. In the past, I have only used lighter fluid for cleaning off finger grime, but this is going to take more than that. Do I start with a moist cloth to wipe off the ash? What should I do?