I've been using pearlite for the last few years. It's the simplest method I've used and there's little mess if any. Just fill a shoebox about 1/2-2/3 full and just pour the water in until you see it about half way up the pearlite. The pearlite acts in a wicking manner, and keeps humidity high without letting the eggs sit on a wet substrate. If the top of the medium feels a little dry, just mix the pearlite and water until it is moiste. Much less mess than vermiculite or peatmoss. Long fiber sphagnum moss works pretty well too, but tends to dry out a little easier.
As far as an incubator goes, it really depends on your climate and how your room is kept. I personally haven't used an incubator to do any colubrid eggs, unless I wanted them to hatch a little quicker. Otherwise I just set them on a high shelf or on top of the fridge........if the temps aren't too high. You really don't need an incubator for kings. Just keep them between 76-86 and you'll do fine.
Brandon Osborne