[JAMF]

As I said, you could start with Paint.NET. I'm doing the instruments with it. The only thing I sometimes miss, is the option to do "perspective correction", as cockpit pictures sometimes have the details I need but not in the right perspective. For that I switch to GIMP. I can imagine skinning could be done with Paint.NET, as a lot is done with layers.

Have a look at skin template too. They can be opened and worked on with GIMP.