If you'll excuse the phrase I'd say go with the flow. Get your hand involved in rubbing the base of his unit and the scrotal area - good when doing the cowgirl or that doggie thing
Even lightly "scritch" with fingernails. It'll be juicy enough for him to enjoy hands on for sure. Also opening your mouth and making moist inviting sounds can help - guys are very visual. While taking your "head" break you might try giving him vaginal kisses up and down his leg/shin and ride the top of his foot. Stay vocal and keep up lots of showtime eye contact and he'll enjoy the multi media event so much any slick willie issues with over-wet womanhood will vanish.