A ground for each coil is redundant. The shielding and baseplate should be connected to ground. Take one of the coil leads- doesn't matter which one, and ground it. Take the other lead from that same coil and connect it to one of the leads from the other coil. The remaining lead is the hot lead. Wire it up and listen. If it sounds really funky, and thin, reverse the leads on the second coil.
Now you have your humbucker wired standard and can apply any standard wiring scheme or coil options.