What kind/size of hook and eye should be used for a full train that is lots of tulle? How do I attach it so it will not show?

If you are talking about bringing it up for moving about more easily after the ceremony, put an elastic cuff dead center of the train about 6 to 12 inches up on the inside that can be wrapped around the bride's lower arm to carry the train to the side off the floor for the most part. It does not show when the train is down, and is not particularly difficult to locate when she needs to gather it up to carry, as it will be much too heavy for hook and eyes if very full at all. If not, make a waist strap to snap it into by adding a couple large snaps at an inconspicuous area under the arm near the waist and snaps inside the lower train.