I always use the inversion method. I watch the Photo I students at my university just move the tank in a circular in a very meek fashion. No wonder they get low contrast prints. I transferred in and have been doing my own development for three years. I don't get what instructor is teaching them.
Anyway, thanks for all of the advice. I have decided to do 1:100 for a single roll in a two roll tank. This will give me 6ml of developer for that roll.