We tried the Whey protein and didn't have any real gains. Maybe about 3-5 lbs over a 2 month period.
Had an exercise and fitness guru suggest we try casien protein. That stuff did the trick. It's a long lasting protein that works over night. My son probably put on a good 15-20 lbs in 2 months.
Directions say every day, we did a shake every other night before bed.