Anyone have experience with coloring latex prosthetics with rubber mask grease paint (RMG)?

Here's my scenario - as usual, I'm all in for Halloween. I have bought latex facial prosthetics online for the past few years and colored them with the RMG that I bought from the company (the recommend you stick with that type of castor oil based paint to protect the latex).

When I got out my RMG this year I've found that a couple of the colors have hardened some, and it's too late for me to order more online.

My questions:

Anyone have any idea on how to revive and soften the RMG?

Any suggestions on where I can find RMG in Oklahoma City? Most of the costume shops I've found appear to be limited to the water / alcohol based cream paints.

Latex mask, RMG, theatre, film, Arts & Entertainment forum...sorry, took my best shot at category.