Glow in the dark pigments are Generally Recognized as Safe, and the FDA does allow them to be used in cosmetics. So it would be just about as safe as every other form of PAX. And yes, mixing glow in the dark acrylic paint with prosaide does work for the sake of making glow in the dark makeup.
That said, I've yet to hear about any terribly effective & safe glow in the dark makeup technique. Most retail glow in the dark paints I've seen have too low a concentration of pigment to be very effective. They tend to look fine for a few minutes, but fade quickly, to the point that it can only seen in nearly pitch blackness.
One trick you can do to extend this is to carry a strong flashlight, preferably one that doesn't leak light out the sides (You can paint leaky sides with a couple coats of black to get this) that uses an array of black-light LEDs or better yet, a black-light fluorescent bulb. You turn it on and hold it against the makeup to do periodic recharges. By keeping the light from leaking, you can do the recharges inconspicuously and If it is for your face, be sure to have a mirror handy to check that you charged everything evenly. Black lights charge up glow in the dark pigment much more efficiently than incandescent light or a CFL bulb. I'd say this method would probably be your best bet. More info on charging the paint here: [url]http://glowinc.com/glow-in-the-dark/light-source.aspx[/url]
If you get ahold of a decently high powered black light and plan to use it frequently and you have sensitive fair skin, you might want to spray yourself with with a base coat of waterproof sray-on sunblock. It will reduce the holding-power of the PAX, but it'll protect your skin from damage. If it only needs a couple small batteries, you're probably safe hitting yourself just enough for recharges throughout a night.
If you like experimenting, you can potentially play around with making higher concentration paint by mixing Liquitex acrylic medium (basically unpigmented acrylic paint) with pure powdered glow in the dark pigment. The powder is ground very fine, and for it to have the greatest effect, it must be thoroughly worked into the paint. For small doses, this is most effectively done by grinding the product together on a flat sheet of glass (such as a mirror) using 2 flat metal spatulas. The grinding action separates the tiny particles and surrounds them with paint. Otherwise, the pigment particles stick together making them ineffective. So you grind it a lot longer than you might think you need.
To tint glow in the dark paint, you can add very small amounts of day-glo phosphorescent pigments. The glowing illuminates the dayglow similar to how a black light works, only less effective. If you add too much, it will mask the glowing making it darker. You can also sometimes find pre-tinted glow in the dark pigment powders.
Most of the time in film and television, they do glow makeup effects via carefully rigged black-lighting shining on dayglow pigments or post-production effects. Once or twice, I've seen a costume where they get the glow effects by rigging up hidden blacklights in the costume pointing at the skin. You gotta be a little careful about this because of sunburn and eye damage issues. Still, done well, the effect can be quite striking.
I've heard of people getting temporary glow effects by taking apart glowsticks and using that as makeup. I wasn't able to find anything toxic about this stuff, but I still can't personally recommend it. At the very least, I'd urge anyone thinking of trying it to keep it away from mucous membranes (eyes, ears, nose, mouth, naughtybits).
Early in the 20th century, companies hired women to paint watch parts with radium-baring paint, which provides excellent glow in the dark properties. They weren't told how dangerous it was and they would paint their nails, skin, and teeth with it. It was truthfully radioactive stuff that was extremely dangerous and gave them a host of maladies often leading to death. The paint is now super highly regulated to the point that you'll probably never see it except on antique watches. So this has absolutely nothing to do with modern glow in the dark or dayglow pigments, I just think it's an amazing story.