[Ian C]

The first four items here are filter wrenches for removing stuck filters from lenses or for separating filters from each other. They’re sold in pairs to separate two filters stuck together.

http://www.bhphotovideo.com/c/search...tialSearch=yes

You can also use a toothpick to apply a tiny amount of petrolatum to the filter threads before installing the filter on the lens to help prevent the filter from getting stuck in the first place.

Here is a wax specifically intended for lubricating metal.

http://www.sinclairintl.com/.aspx/pi...perial-Die-Wax