My method is demonstrated above. I start with a rough pencil sketch of the subject which I scan in and fill with a skin tone (65% fill) and then paint over the top of it. I do it all on one layer unless I'm adding glasses which I'll draw on another layer. There is no 'magic' involved in fact it is pretty close to normal painting. I don't use a huge brush and block in areas, as some do, I slowly fill each area and use a limited skin tone palette. All up the face is around 3 hours work - perhaps longer - rarely in one sitting. I usually have about six commissions at any one time and I hop from one to another - you get tunnel vision looking at the same painting all the time and often coming back to it later you spot changes that are needed you couldn't see before.
I only use three brushes for 90% of painting. I used to use a massive array but got rid of them bit by bit. Altering the Brush presets gives you much more versatility.
( Larger version of the WIP is HERE)
I use Photoshop, CS4, as my tool of choice and also use Artrage for preliminary work. If you moving down the digital path and want to start out without the expense, and complexity, of Photoshop I can thoroughly recommend it - Check it out HERE.
I have used Painter IX, which some people swear by, I've never warmed to it, the GUI is far too complex and it isn't as intuitive to use as good old PS. I'm also too old to learn a new set of keyboard shortcuts.
Oh, and naturally I use a Macintosh !! (I'll get a bite there from someone ........ )
The WIP above is a current commission which I will post when the whole theme is completed.