First you want make a point of telling him that you are going to rock his world by milking his nuts. Next, with your eyes straight on his and your hand cupped slightly, reach under his throbbing cock and separate his nuts with your middle finger while cupping them with the ring and first finger, thumb and pinkie. Make sure that your middle knucle is placed on either side of the middle of each nut. The with a slight upward thrust, roll his balls into your palm and squeeze gently but consistently in a pumping action until he tells you they are starting to ache with "blue ball syndrome". Then release his nuts and suck them into your mouth and lick them in the warmth for about a minute. After the minute is up take each ball in between the first finger and the thumb and middle finger and working toward the rear of his balls milk the ball by pushing the sperm out through the back toward his vas deferens. Repeat this milking action ten to twenty times squeezing harder each time. As his cock starts to pre cum from the extreme need to ejaculate, place your finger and thumb in a circle shape and pushing over the throbbing head catch the globs of precum on your circle shape and push over the ridge until your fingers are tightly around the space just below his now fully engorged head ridge (and it will be because the milking action makes the head ridge really big) and start milking his shaft in 1/2 inch squeezes and twists while alternating pumps of his balls with the other hand until he cums. This method is called milking his nuts and will produce an unusually large thick load of cum because his semenal fluid gland will respond to the forced milking of the sperm into the ejaculatory flow. He may even experience a double ejaculation which will blow his mind and leave you with a very satisfied stomach.
Mandy enjoyed milking his nuts because of the huge loads she got to eat.