One trick i learned from a groomer while in vet school was to always start trimming a dogs toe nailes from with the hind legs. Dogs are more sensitive about their front feet, so you can get half way done before they know it.
Another trick for dogs that are really bad about nail trims, but will tolerate a bath tub is to put enough water in the tub to cover their feet. then trim the nails under the water. The water will soften the nail and the dogs for some reason will tolerate it. Just be careful to not cut the nails too short becuase the angle can be difficult.