I`ve used tablets in the past, but they are no good for creating skins, i think.
A vector based program, such as CorelDraw or Illustrator, is way more easy to create precise curves with a bezier tool. Its like the path tool in Photoshop.
I draw the whole skin in Illustrator, with a locked template of the xxx_default skin, and when its finished i just copy and paste it in a new file in PS. With CorelDraw you better export it as a JPG.
Sometimes I do the final touches in PS, such as shadows, color correction, etc.
This way the final job is much more neat, IMHO.
I attach some samples.