A good tip for even the fast moving rats. Take your hand and put it over their head to their shoulders, from the front. Scritch the shoulders/neck...often they will start to lick and groom you with their teeth as you hit The Spot.
Our girls like behind the ear and on the cheek (sort of), just up from the corner of their mouths. Our youngest also likes a belly tickling occasionally, and a pinch and rub of the skin on the back of her neck.