This I think is one of the better pieces I've done recently, and it might have been because I was put under a bit of time pressure - this was started about 5pm one day and had to be finished by the same time the next day. As it turned out that wasn't a problem, but it got the nerves tingling a little bit!
I was sent a really good quality photo of the subject (who's a CEO of an energy company in the U.S.), but as I wasn't familiar with him at all I looked up a few more photos to get an idea of his face structure etc. It took a few goes to get a sketch I was happy with:
I got the go ahead to carry on and quickly blocked in some colour:
Then the following day I painted for 5 or 6 hours roughly to reach the final you see above. Here are a couple of details. After finishing I added a little bit of noise to the image with a Photoshop filter - I've seen other artists use it a lot and never really got it, but I used it for the WSJ in the previous post to knock the background back a bit and tried it on the painted face and it looked good, I think maybe it's to do with the size and level of detail in the painting being enough to take it.