The last one is mine. I basically just started with a hard brush of a strong color then lighten the color and use a soft brush on top. After you've got your render positioned the way you want it use a soft brush with the layer mode set on linear dodge.
The other thing is lighting of the render. Most people use the light that is already on the render and just build around that. I actually change the light around myself usually using multiply and soft light layers. Hope this helps.