I used Krylon aqua colors (because it's hypoallergetic and doesn't irritate my skin and such)
and I used that on my face to mid neck)
I also used I Ben Nye's final seal spray over it THEN in addition used translucent powder (you can also just use baby powder)
Then I got pros aid and mixed that with gray acrylic paint and painted up my arms/neck.
Then LOTS of powdering, especially in the elbows!
The wonderful thing about prosaid is that it doesn't wear onto your costume. That's why I used it around my neck/collar because then it didn't rub off onto my shirt.
The only problem I had was removing it. The prosaid remover smelled AWFUL (I would NOT suggest spraying it in a confined space- or even a hotel room like I did!)
I got wonderful results, though. And didn't rub on anything.
For results of my Equius cosplay check out my deviantart (below). I'll also be uploading soem more pics soon!
Any questions feel free to PM me on here, my deviantart, or even tumblr.