Asi I seem to spend quite a bit of my time on experimentation (finally working on production for my first little show after ten years of dedicated work in clay, sheesh), this is one of the things I've done, but put on the back burner to practice my trailing hand skills.
I didn't find color intensity to be a problem, as bcsiske notes:
The difficulty I see with mixing wax and glaze is consistency in color value. If you don't nail the color with the first brush stroke, your out of luck as the wax prevents adding a second or subsequent stroke.
The wax does apply to itself, so you can go over spots with the trailer or a brush. To find the intensity, of course, test, test, test before applying it to your mistress-piece.
However, mistakes are tricky. It stays where you put it, and the stain/mineral colorant will be there even if you redo fire the wax off.
What I found most successful was to take a smallish amount of a liquid wax base (something a little stickier like Laguna worked better than the thinner waxes), dollop in either some LUG1 black underglaze, or black iron oxide, or cobalt carbonate (the cobalt oxide is just too strong), and mix it in a small needle trailer. Where you trail, your wax will resist most over applications of glaze. I take a small water-wet paintbrush and wash/push the glaze off of the lines. It helps if your over glaze is thinner vs thicker.
There are commercial products that have formaldehyde in them (I just did a quick search but couldn't find it) but as I am ghastly allergic I just tinker with my own. Hate the fumes. I did not take the step of buying commercial black wax resist to try them out, as my results were great.
As for glaze=>wax=>glaze, I found the over application of the wax to be trickier. It was hard to control the glaze-free barrier space... Sort of like doing precision hand work twice over the same area was too much skill for my hands. Perhaps not for you.
Fun to play with: good luck with your tests.