The UV protection is also good for helping prevent yellowing. If you're just doing eyes or something small, acrylic sealer is probably easiest. I like to just mix it into the paint, it saves a step, & I find it makes the paint go on more smoothly. Also, I only use matte finish because to me, the shiny finish is too shiny for my tastes, the matte isn't actually matte, it's just not really shiny. I guess that probably has to do with using it on plastic. I can't believe they told you to use hairspray, I would think that would cause pitting on the plastic.