About Sisko's hands - I think the best tricks are already mentioned. Either to clone the color from his head and putting a layer with 25% (or so) transparency on the hands, or trying to decrease lighting + contrast and fiddling with color-balance.
I guess the best way is simply to try and see what works best. One option is, of course, to search a pic with Sisko's hands showing and using them in this pic. Maybe there is a pic of him on Defiant you could use? Either way - good luck! One part of "the fun" is trying to solve these kinds of tricky situations.
Well, some of you might already know that I am a J/Cer through and through. So majority of my fiddled pics are about J/C. Since I have not used Mark, Janeway's ex-fiancÚ, before I decided to give it a try. This pic is called "Tension". (Yes, I name my pictures. Ha ha. The above with Picard and Bev is called "Dinner in France"