I like lotion on the soles, but on the rest of her body I like slipper and messy oil. I like how her curves glimmer when she's oiled up. Seeing a woman's curves accentuated like makes it all the more irresistible to get to tickling action.
Not to mention oil works great on ultra-sensitive parts like her nipples, it makes it less painfull, but it doesn't take of her sensitivity to tickling and overal enjoyment.
What also works well is your own saliva, but that's not most women like to have on their body. It works the best after you have drunk fruity juice (preferably grape or apple) followed by consuming a bit of lemonade (it makes you saliva thicker, yet only a little sticky if you're easy with the lemonade). Still it's a very dirty business, but neither her nor my saliva don't gross me out at all when I'm horny and it works for making her body slippery and ultra-sensitive. ^^