The very usefull tricks shared by WWSandman and Solo are bit hidden, so I decided to put it as a sticky right here.
You're not sure if you have all the required skin folders or you know you miss some of them? There's an easy way to get them all in one shot

Use this tool:
http://www.sas1946.com/main/index.php/topic,4278.0.html or
even better:
Use Solo suggestion to create a 'bat' file. By pointing it to your air ini file, it will create every skin folder your install needs (and only those, so no extra skin folders unless you have garbage in your air.ini). I quote (Solo):
"Just a little MsDos command to extract the names of \Skins folders directly from air.ini
Copy the following line into a *.txt file and rename it *.bat
for /f "tokens=1" %%a in (air.ini) do md Paintschemes\Skins\%%a
Put your air.ini and the *.bat file in the same folder and launch the *.bat file
Magic !! , for each plane listed in air.in ==> his Skin folder
Delete the Paintschemes\Skins\[air] folder and copy the Paintschemes directory in your IL2 install
That's all."
EDIT: I add Bravo's link to C6 batch file as well:
"There is a Batch File for creating Skins folders at C6
http://www.checksix-forums.com/showthread.php?t=160057 Post #19 "Skin4.zip" "