I think wetting it is a good idea too, and the nail clipper idea sounds good, just be super careful and have steady hands. I use a fine wire cutter to do the same thing here and there. But I find it is usually the best to take one hand and use just the pointer finger and the thumb to GENTLY hold the cotyls, then with the other hand using the same two fingers GENTLY grasp the seed casing.
When you pull them apart, you need to just barely try to "slide" it off. If it doesn't budge, you have to chose to either force it or leave it. If you force it and the cotyls cut/break in half, then the plant will likely survive as the next set of leaves are surely close to follow. But if you pull the whole cotyl leaves off, the chance of survival drastically decreases.
On the other hand, if you just leave the seed casing on, then one of three scenarios will most likely occur... 1) One of the two cotyls will slide out naturally and the casing will likely be stuck on the other - no problems here, the plant will be fine 2) The casing gets pushed off completely and naturally - least likely scenario, but would be the best to occur, the plant will survive 3) The seed casing stays stuck holding both cotyls together - the problem is the new leaves aching to grow out will either help to push the seed casing off, or the new leaves will be light deprived and could mold or rot. Also, if the new leaves don't make it outside of that "cotyl taco," the plant won't likely be able to get that whole photosynthesis machine started and will probably cannibalize the cotyls first, and eventually die.
This is not a claim that I know everything, I may very well be wrong. So remember, the final decision rests on you!
If it were me, I would try to pull it and learn from experience.