HST does not have specific dietary requirements. If you want to put on weight you eat surplus, if you want to lose weight eat below maintenance. How to eat (partitition, timing, supplementation) is beyond the scope of HST. That said, the gallon of milk thing is good in my opinion. If you can (are not lactose intollerant for example) milk is a great source of protein, carbs, calcium and is cheap(ish) and practical. You can use skim milk if you don't want too many extra cals. The recommended carbs after training are slow digesting high-nutritious carbs. They will be slowly digested throughout the day providing a steady stream of carbs in the blood along with important nutrients and fibers. So yes, follow those recommendations but remember to calculate the number of calories to certify yourself you are at your target cals for your goals, either gaining or cutting.