Newbie top hand grip question

When you do basic spins, are you gripping the pole (with top hand) with your thumb around the pole as if it's a baseball bat, or do you let it wrap around with the rest of your fingers? I notice I am letting it wrap around (kind of like I am 'cupping' the pole with my whole hand and thumb), but that gives me very little grip and I tend to slide down quickly. But when I try to wrap my thumb around, it tends to stop my spinning.