Grooming should be considered by both of you as an enjoyable experience. Lay your puppy down on his side and tell him “STAY” in a firm but affectionate voice. You will definitely have to struggle with him to begin with but remember you are the boss. You will most likely have to start out by holding three or all four of his feet with one hand while you brush with the other.
Gently brush his side and tummy while telling him “GOOD STAY” or some such phrase. This should begin as very short, gentle grooming and not particularly serious. As he gets used to the position, he may even take a nap during the grooming session. Finish up by giving him a treat.