I was asked how I did this:
without ruining the factory paint.
Like always, my answer is L.A.'s Totally Awesome.
This Twilight Sparkle has nail polish all over one side and I'm going to pretend it's on the paint for the purposes of this tutorial.
We don't want to get acetone on the factory paint, so instead, we soak that part in concentrated L.A.'s Totally Awesome straight out of the bottle.
You know it's working when there's discoloration or the nail polish starts peeling of.
Wear gloves. Totally Awesome will make your skin sad.
And then you just scrub with the toothbrush until the nail polish is gone.
Resoak, scrub more, repeat as needed.
It's not a fast process, but it works.
Like I said, wear gloves.
This stuff is kind of unpleasant smelling.
There is always a risk of damage to your pony, either to the vinyl, factory paint, or the hair. There is a risk of the nail polish staining.
But that is how I got all that nail polish off of the little Rarity figure without affecting her factory paint.
L.A.'s Totally Awesome can dissolve nail polish, acrylic paint, Mattel's head glue, G1 flocking glue.... It's pretty handy.