What I've done with my gliders, is always find a CoG and then back it up a bit, depending the size of the bait one to two or three millimeters.
When you've done a quite few of these, you'll start to get hang of it and kinda "wing it".
Coating materials that I constantly use, adds up a bit weight and are heavier than water which means that coating always, and I emphasize, ALWAYS moves CoG towards the nose.
On the opposite end, when you use coating with density less than water, it moves CoG towards the back as it adds flotation of the nose more.
Why? Well basically no matter what kind of glider you make, bait has more surface to be coated from mid to nose than mid to tail.
So after you've done a few, you'll just wing it after initial measurement of CoG and move it millimeter on three towards nose or tail.
Another thing I'd say, and this is just my opinion and depends what kind of leaders etc you use... As they usually add nose dive rather than lift the nose up, so if you manage to screw up balancing the lure, it's in my opinion, better to rather nose up than nose dive a bit when gliding.
So moving CoG towards the nose just a tad is almost always better than moving towards the back. Trying to get it dead center is usually prominent of tipping nose down.
Cheers, Jarmo from O'Baits