Lint cant get into the valve body because the fluid goes into the pan and its sucked up as its going through the filter into the valve body.
I have used paper towels my whole life and even newspaper, I havent had any problems with that.
My dad always told me to make sure you get the old gaskets off, and the one time I didnt check, plow, there goes 5 qts of oil all over the floor. haha.
When I changed my tranny fluid those cork gaskets like to stick so be extra careful with those.