In addition to all the good advice that youāve already gotten, remember that you have a lot of power available to you through the Draw/Alpha/Tool palette combinations. When Iām texturing, I always use a pretty low RGB intensity, with all else turned off (MRGB/M and ZADD,ZSUB,ZCUT). A low setting lets me add color a bit at a time, to get better variation. The only time I turn M on again is to switch to a material with subtly different settings, as Southern teaches. All of your 2D and 2.5D brushes can be customized using the Alpha palette, giving you an infinite variety for just the right effect. Finally, you can change your stroke type ā which is very effective in places.
If you reduce the specularity on your material and add just a touch of color bump, youāll have awesome skin, I think.
All of that said, I see nothing at all to complain about with this. Itās a really great image, and I personally like the fact that Peter is starting to show a few years. Marvelous job!