Should you, and how do you, grease a crockpot?
Personally, I've never made a dish that required greasing of the crockpot - even if it called for it, I've ignored that step and had no problems.  I can only imagine the step is added to ensure nothing sticks - but my crockpot (and all others I've seen) are glazed porcelain or ceramic, and the recipes always include a liquid of some kind, so I don't think that's going to be a problem.

If I were going to grease it, however, I'd do it in the method you described, and use a very light touch.