Use tongs to prevent piercing the casing with a fork and causing the juices come out. You will dry the brats out and lose a lot of the flavor to the coals. If instead of parboiling you take the fresh brats straight to the grill, be sure to cook them slowly over a low temperature. If the coals are too hot it will be almost impossible to fully cook them on the inside. It's worth the wait so go "slow & low."