Tom, you are correct about that being much easier, but using Vasoline is the official lubricant for potable water, and I assume we all appreciate potable water to take a shower with.
In all honesty, Tom's method exposes the human body to so little questionable chemicals, I would think that is fine.
Ron, the next time you in a hardware or plumbing store, ask them for some plumbers grease. Most likely you will get a silicone grease from them. My plumber uses it our house filters and water neutralizer seals. Also doctors and dentist all use silicone gloves now a days. I would think that silicone is safe for use in a shower. Maybe even better than the old, used for many years, Vasoline.