Actually, surprisingly no prior gym training would be a benefit in this situation as his gains for the first 2-3 months would far surpass a person who trained regularly until they hit the wall where the body becomes accustomed to it.
The more muscle you gain and the more the body becomes accustomed to lifting, the less muscle gets broken down and the harder it is to gain more. You should know this having lifted for 20 years, it's basic physiology.
Same with protein...people think as they get bigger their body needs more protein when it really needs less since it's become hyper-efficient at using it and they are breaking down less and less muscle.
I had a lot of experience with lifting but the fact remains it certainly is possible at that age as I did this from the age of 38-45 every single year. Looking back I realize how idiotic it was to bulk and then cut since I ended up in pretty much the same place but better late than never in terms of figuring that out.
The cheat day greatly helps with cravings and allows the body to refeed and not have any chance to even think it's starving. I used to look forward to that day and literally plan it out...ice cream in the morning, taco bell for lunch, pizza for dinner...it was an all out food day.
He asked for the fastest way to accomplish it and I gave it to him. Is it difficult? Somewhat, but once you start seeing the results after the first week it starts becoming a lot easier...
