Hey Spookzilla, basically any liquid latex applied as described by bw1 will give the effect of crinkled, wrinkled skin...but there is a specific product that I have had good success with in the past, it's called "
Fake Skin" and it is made by a co. called
Living Nightmare. I've used it both to wrinkle and age my skin ( I know, MT, weird, huh? Most days I'm buffing and moisturizing to make it smooth!!

) and to give the effect of skin peeling away. Spencer's carries it every year, and it's also available on line.