Ordinary drip grind is about right for pressing 3 scoops. But for single servings, espresso grind will give you more flavor for your money. I often set a grinder about halfway between drip and espresso. You can do that at home if you grind at home, or with the your store's grinder.
If pressing takes longer than 60 seconds, use a coarser grind. If it presses faster than 30 seconds, a finer grind will give richer flavor for the same amount of coffee.