Put antifreeze in black and grey after winterizing ?

There's no need to put antifreeze in empty holding tanks. Air doesn't expand and cause things to burst in cold weather. (Even a little tiny bit of water left on the bottom won't cause problems when it freezes; it has plenty of room to expand.)

If you have excess money that you don't know how to spend, and you don't want to send it to DrewE, you can buy more antifreeze and pour it into the tanks and it won't cause any harm...but it's not at all necessary.