It is recommended that you use a mask when dealing with Spectraflair. If I were making large quantities of anything and had dust flying, I would. I don't feel it's necessary to franken a tiny amount of gel polish. I have several other "car paint pigments" and I've not had any fingers turn green and fall off, I've not had any reactions, etc. However, if you are concerned or not comfortable using this, DON'T. I am not recommending anyone try this or use any other product that isn't intended for use in nails or cosmetics, this is just my personal experience and what I do.
Spectraflair is a very, very, VERY fine powder that has a holographic effect. It actually comes in a few different particle sizes, from 20-35 microns. What I have currently is the 20 micron size, but I'm trying to get some of the 35 micron size, as it is supposed to be a bit more blingy.
The Spectraflair isn't a super-bright, obvious holo. Indoors or not well-lit areas it just looks shimmery. Outside or in well lit indoor areas however, it creates a very nice holo effect. The holo effect is more predominant when used over a black base or other very dark color.
I've mixed Spectraflair into Structure gel and also into a few colors of gel polish. It seems to work fine either way. With the structure (or you could use TIO), you can mix a tiny amount to make a more sheer topcoat, or you can mix a slightly larger amount in to get an opaque silver color. Either way, the amount you need is REALLY tiny!
For this Manicure I mixed up the Spectraflair with Gelish's Up in the Blue
Here is a close up of one of the nails:
Here are some other samples I've done:
From left to right: Spectraflair mixed into Structure to make opaque, Spectraflair mixed with black and painted over a black base coat, Spectraflair mixed into Gelish Up in the Blue (I used a bit too much spectraflair here, but it came out great when I did the manicure), Spectraflair mixed with Gelish Exhale
Here is a the video on mixing spectraflair with Structure, but again you can use any color you want to mix with. Or, you can apply any color polish, then use clear mixed with spectraflair as a topcoat over it. :)