This is what I've done before:
Assuming a Fri weigh in, drink a gallon of water Tue, 2 gallons Wed, 3 gallons on Thu, cutting out all liquids and food 18-24 hours prior to the weigh-in. If your weigh-ins are early on Fri, it may be very hard to get in that 3 gallons 18 hours prior, but do your best.
You will likely gain a little weight on Wed and Thu morning, but by Thu you should be peeing every 15 min. This will continue even after ceasing water intake. If you feel you need to, you can also add in hot showers, homemade hotel room saunas and/or sitting in your car w the heater on as the weigh ins get close.
Post-weigh ins I'd drink a gallon of water before eating anything. Some people prefer pedialyte or a 50/50 mix of water and gatorade. When you start eating, I'd strongly advise you to stick to whatever you normally eat. Some people think they need to go w junkfood to get in a lot of carbs, in my experience that upsets my stomach. Be sure to add salt to your food as well. That's as far as food and drink choice goes, I hope it goes without being said that the amount should be as much as you can
15lbs is a lot to cut for a 200lber, but I dont think you need to go all the way to 207, maybe 210 should be enough? I wouldnt be in a caloric deficit for the week of the contest, but if you have any experience w low- or no-carb diets, you can institute that in order to deplete glycogen.
On the one hand it's pretty simple, on the other hand there's lot of personalization and preference for different methods, let me know if you have specific questions.