Sadly, this was originally tried with natural light - but there was not enough of it, so I had to use the flash. I didn't think to use my add-on flash though, which apparently shows and hurt the score.
I love their wrinkles! I think the comment that aKiwi left is a good one if you can get a chance to try shooting in natural light. Hard to do when one works during daylight hours, though, and especially hard if the weather doesn't cooperate and provide any light!
On camera flash doesn't help this image.
Try to ues a more imaginitive lighting setup. Either try to get your flash off your camera, or use window lighting or a reflector to make things more interesting and softer.