I don't like to use anything, no water or oil. It just makes a mess, and is not needed.
I usually use an Eze-Lap model L to sharpen my pocket knives. I cut off most of the red plastic handle and it fits in the zipper compartment of my wallet. That way I can touch up my knife anywhere, at anytime in a few minutes. Sometimes, I'll finish it off by stropping on the back of my belt.
If I'm at home, I use my old boy scout gray carborundum stone just for yuks sometimes. If I strop it afterward, it still gets hair shaving sharp on that old pocket stone.
Carl.