I have found that using olive oil, light olive oil does the trick. Olive oil is the purest oil that we can use. We cook with it so it stands to reason that we could lubricate with it also.
Personally, I use it. I just use an eye dropper, draw up a little bit in the eye dropper, insert it, be sure to use a paper towel or something to catch the extra that your body doesn't need.
Your good to go, fast easy, works REALLY well, if I do say so myself. I have to use it every couple three days, but it is worth it.
Many people swear by coconut oil for this purpose. It has a pleasant odor and is very good for your skin.