I recommend sliquid silver. This is a silicone based lubricant that is marketed as a sex aid but it also works as a general purpose skin lubricant. It is waterproof and lasts a very long time. It seems expensive at about $25 for an 8.5 ounce bottle but a small amount is all it takes. I used to use petroleum jelly but this works better, is not nearly as messy, is lycra and elastic compatible, and comes out easily in the laundry.