Here i do a quick sketch, i usually sketch out the skeleton first but you cant really see it here. I then add the muscles in his face to create some sort of age look.

When i outline it i usually give muscles a quick check over and then outline it.

My favourite brush to this is probably this. Its good for blending without the use of a smudge tool. I have the flow on low so i can have it light in areas and darker in some.

Depending on what the background i have, i use a dark base so i dont get the colours wrong for the background.

finished version: http://www.deviantart.com/view/25469083/