I think that cheap throw away plastic tarps thrown over a mattress, or floor, would probably work very nicely.
I invested in a play mat from the Liberator company a few years back.
http://www.liberator.com/black-label-escape-wet.html
When I'm done with it, I stick it in the shower and wash it off with soap and water. But unless you're going to be doing a bunch of messy play, it's probably not worth the trouble.
I'm much older than many of this group and I remember the vegetable oil fun. I didn't do it a lot but I did do it.
I would probably go with grapeseed oil or a more commercial/organic/Nuru massage oil instead of the vegetable oil.
But heck, whatever works, right?
My cheap nickel advice for the day: When doing messy play, keep a few clean towels within reach. Especially when you're slipping and sliding all over the place. With my mat, if things are really slippery, you HAVE to have that damn towel to get some traction going if you wish to delve in a different direction.
Or reach for a condom.