Ok, I know something about this, having done it for posters and such. This is not something you want to do. IF you are already very lean, and have decent muscle mass (some of which you are going to lose). It's 2-3 weeks of strict dieting, having no energy, and feeling like a pile of steaming shyt. Then, in the last few days, you begin to dehydrate, and deplete all the carbs from your system. The day before the shoot, competition, or whatever you are prepping for, you pig out on carbs, thus hyper-inflating your carb starved muscles with glycogen. Then 15-30 mins before, while in this half-dead state, you do a workout and get pumped up. All for about 2 days of ripped glory.
Don't bother, end of story.