You should NOT have to use baby powder to get it on. That can be counter productive. Powder makes things slide. It might be easier to get on, but you don't want to have the shirt slipping on your skin when it is on. The only cases that powder might be needed is for people that sweat a lot. It is very difficult to get a tight shirt on a sweaty person. If you don't absolutely have to use powder DON'T use it. I have gotten people into very small shirts that seemed inpossible to others.
Your best bet to get into a tight shirt is to get help from somebody that has done it before and knows what they are doing. It might seem crazy to you, but is probably not that tight.