I found one pack of Zinker Zs locally and want to try them on the Ned rig for bass tomorrow on the river. I need every big of the bouancy I can get out of the bait. Hearing that they get more bouayant with use, should I rig them and put the rig in a mason jar of water for a couple of hours?

Don't rig them. Stretch them several times then soak them in water overnight and it should get the salt out of them.

Wow these baits feel strange, got them soaking for tomorrow's fishing.

How careful do I have to be with other plastics if I fish both on a trip? Will hand sanitizer or a rinsed in the water be enough to not screw up either?

Just don't store them so they're touching regular plastics (leave then in the package), and you'll be fine. You don't have to wash your hands between handling them or anything crazy and they don't melt instantly, it's a slow chemical reaction.