I scan lots of documents through my sheet-fed ScanSnap scanner every week. It does a decent job of separating the sheets of paper but sometimes the pages will stick together and go through the scanner at the same time. Luckily, the scanner has a sensor that can tell when more than one sheet of paper has gone through and displays a warning. When the pages stick together, I have to slide them apart and run them through the scanner again. Sometimes the pages are stuck and my dry fingertips can't slide them apart. I could lick my fingers, but it grosses me out.
Instead, I use this stuff called SortKwik. It looks a little like underarm deordorant and feels a bit lit it. But it gives my fingers enough grip to be able to easily slide two sheets of paper apart. It's not sticky, it's just "grippy." A little goes a long way. The container I bought has lasted for years. (I initially got it for doing card magic, and it works well for that, too.)