Photoshop :: Making A Person Skin Using Gradients, Patterns...

I know it´s possible to create new characters for realistic games, Mangás and even presentation, simulating pure skin, as in people using trunks. They can preserve the face, feet, hands and even chest, however they do limbs entirelly from scratch. I know they use the ´copy area´ button, but some skin can be made from the beginning, by means of noise, patterns and gradient. I would like to know some of these techniques

I´m almost expert using ´copy area´ effects until now, but I do know it´s insufficient for a good artwork. Some limb areas still looks ´repeated´ and ´painted-like´.