This is incredible, 100 years of airbrushing history and suddenly they need to be laser guided,
, why not let's have April fools day every day in april
As well as trying to find something small and light enough to attach to an airbrush without knocking it out of balance, calibration would be a huge problem, getting it to be able to see past the head of the brush to shine on its target would require it to be mounted high above or very low under the brush, even then, it would have to be self adjusting to be able to remain on target since the beam would veer off course when distances to substrate were changed, and as mentioned, the problem of a fine enough beam to be useful in any way and interference with colour perception would be huge factors.
I'm not saying this couldn't be done, but if the time spent making it possible went into simple practice instead the precision sought would come on its own a lot quicker and no one would need to look rediculous while working
I hope you do manage to make one, I would love to see it just for the novelty aspect, and we could maybe change your name to "Airbrushing Sniper"
Note also that the laser in a DVD device is a class 1 laser product, this means that it is only safe as long as it remains in the device, if it can burn data onto a CD, it can also burn your retinas, and you don't even need to point it at your eyes, it will do that on its own when it reflects back off of your glossy wet paint, which will mean that target practice will be the least of your worries