I had this as a post...but just so it's at your fingertips I wanted to add it as a page.
I have been getting many questions regarding makeup, paint and adhesives so just wanted to add my two cents here, but feel free to contact me if you want more clarification.  And please don't hesitate to comment if you have any words of wisdom or feedback as well.  I always love to hear other folk's makeup "tid-bits." 
My makeup of choice is a water based makeup called Aquacolor from Kryolan located in San Francisco, though they have worldwide retail stores. It blends beautifully and is easy to apply both on the prosthetic as well as the face.  This can either be painted on with a brush or blended with a sponge.  Just add water.  Other brands carry similar products such as Mac and Ben Nye, but I have not personally used them, so I wouldn't be able to vouch for their quality. 
I also tested painting a prosthetic with liquid foundation.  The outcome was fine, but not nearly as flawless as with Aquacolor.  So...for a quick fix, use liquid foundation. 
RGM Paint(Rubber Grease Mask) can be a bit difficult and sticky to work with...in my honest opinion...but the colors are vibrant and very opaque.  The method I used most in college on foamed latex pieces was to mix cream makeup with castor sealer/oil...same difference.  This is a sufficient replica for RGM paint, but make sure not to add to much castor sealer, otherwise you're in for a mess...I learned this the hard way.  The trick I used was to cover the prosthetic with a light layer of castor sealer and then painted with the cream makeup blending as I went.   

I use a homemade product called Pax Paint, this is a 50/50 mix of acrylic paint and Pros Aide (prosthetic adhesive) which gives the acrylic paint elasticity.  Do not, however paint your face with this material.

My adhesive of choice is Pros Aide.  This can be a bit expensive, but not nearly as expensive as some products on the market.  It is gentle on the skin (as well as on the prosthetic) and if applied properly is quite long lasting.  The one downside to Pros Aide is it does not have a proper remover.  What I find works best, and is quite effective if I do say so myself, is mineral oil.  This can be found at any drug store near the hydrogen peroxide and rubbing alcohol.  Let the mineral oil soak into the sticky residue and with a warm, damp cloth rub your skin in a circular motion.  Do not pull.  Add more mineral oil if needed. 
Spirit Gum is most commonly used and is quite inexpensive, but I try to stay away from this stuff as humanly possible since I am allergic to it.  Though, don't let that stop you from using it...I am one of the very few.

Hope this helps.