I have used the same figures you have as well as the tamiya 1/20 scale as well for my F1 dioramas, A variation on the flesh colour from Tamiya is good -Tamiya flat flesh XF-15... what I mean by variation use slight amounts of flat brown and the flat flesf to achieve desired results around the eyes and cheeks and wrinkling areas..
I also have this great book on dioramas and figures if you want I can scan that section for you....
check some stuff I have done...
http://www.angelfire.com/de2/darren/brab.html
http://www.angelfire.com/de2/darren/sub.html