Pretty cool, but... there's no way I'm rubbing petroleum jelly all over my lenses!
I had almost worked out the ND filter myself, except for the mounting challenge, and that was answered here.
Good share!
He used a UV filter, which can be had for pretty cheap. I had always heard about doing this but I felt the same way till I saw this and realized he was using a filter. I like the effect and might try it as I have a few UV's that are not being used.