I think this article is super helpful for answering your questions, and may also be directly useful to your client, though it sounds like he's pretty much already made weight w/o issue: http://www.elitefts.com/documents/making_weight.htm
Has this person ever competed before?
From the article: (which assumes your client is cutting water, which may not be necessary)
"Immediately after weigh-ins, start drinking water again. Drink at least 16 ounces of water. Then eat some high energy foods. Focus on quality carbohydrates like oatmeal, apples, apple sauce, or bananas on meet day. Include foods that you enjoy because they are easier to get down if youâ??re nervous. I love peanut butter and jelly sandwiches on wheat bread. They taste delicious and theyâ??re jam packed with calories including carbohydrates and fats for energy. Avoid sugar-filled and high glycemic carbohydrates like grapes, watermelon, candy, and fruit juices. This will spike insulin levels and lead to a crash. You want carbohydrates that will provide sustained energy.
You can eat a candy bar when you get ready to deadlift if your energy levels have dipped and you need a quick boost. Thereâ??s no need to concern yourself with protein on meet day. It takes too long to digest and can slow you down. Lastly, itâ??s important not to change too much on contest day. If youâ??re not used to eating pancakes with syrup, then donâ??t all of the sudden eat a short stack before you lift. This could potentially wreak havoc on your stomach. Eat foods that are familiar.
After eating your first post weigh-in meal, drink another 16 ounces of water. Then you can introduce sports drinks like Gatorade, Cytomax, or even Pedialyte. There has been research supporting how ingesting a lot of sodium and potassium via sports drinks immediately after depletion can be dangerous. The good news is that if you follow these simple steps of proper hydration and sufficient caloric intake you wonâ??t be dehydrated nor depleted of electrolytes. In fact, youâ??ll likely be exactly where you want to be. So, in this situation, the sports drinks arenâ??t dangerous.
You can also eat salty foods like plain salt, potato chips, or canned chicken soup or drink a V-8. All of these are ultra high in sodium and will be absorbed quickly so your body will begin to retain more water and then your gear might even fit a little tighter.
Overall, the plan is fairly simple once you have an understanding of basic physiology and your bodyâ??s response to food and water. Lifters make the process out to be more than it is. If for some reason you get in a bind the last week and have difficulty losing those last few pounds, you can use a mild, over-the-counter diuretic like Absolute Nutritionâ??s Watershed or Eclipse Shrinkwrap Definition. They are potassium sparing and donâ??t contain stimulants. Because some powerlifting federations prohibit the use of diuretics, always consult your federationâ??s drug testing policy. The key ingredient in your diuretic is uva ursi. Uva ursi comes from the leaves of an evergreen shrub and is used to treat common urological issues like urinary tract infections, bladder inflammation, and kidney stones, thereby having a diuretic effect. Dandelion root is another herb with similar effects. Vitamin B-6 and green tea help too."
Hope this helps!