What program do you think is best for skinning?
Adobe Photoshop is my personal weapon of choice, tho alot of people use paint shop pro.
House Quake has a pretty good review thread over on the NPI forums for the programs you can use, check this link to read it:
http://newpowerinc.com/original_freedom/viewtopic.php?t=1032
I also use Adobe Photoshop for skinning but there are other programs you can use that have similar features. Also i use a lot of plug-ins to create certain effects, like Eye Candy and Xenofex
I wanted to add I use photoshop now because it's what I have but back in the days when I used Paint Shop Pro it was great for skinning, really not a step down from photoshop. Beyond that just get yourself some base skins and start playing around, figuring out your style. Check out the tutorials too.