Depends on the layout of the fridge. When something like that happens to me (would have to be an old fridge as all the current ones here have solid shelves) I find pouring a little baking soda over what I can of the spill itself, wait a few hours for it to absorb any liquid and then with a paper towel or two at the bottom, chase the spill with a bit of warm water. Most of the time this works for me. When it doesn't, I repeat it again and that usually fixes the issue.