Canaris first thing you need is some type of paint program. Many use one the two most well known, Paint Shop Pro and Adobe Photoshop. There is a list of other programs out there like Corel Photopaint which will also work just fine.
Secondly you need to "save" your skin. Go into the game, click on the hangar. Select the plane you like then right click and hit save skin. This will place your skin in the skins folder in the AH2 directory. If you did a normal install and didn't change the location of your install this will be the file location. C:\Program Files\HTC\Aces High II\skins.
Go into your paint program and open a new file. Search for the directory I stated above and find a fold inside of there that would say something like, "p51d". As an example these are files you'll need to open from that folder, P51DSID and P51DWNG. These two files have your main fuselage and wing areas on it.
Now if you plane on completely redoing the skin you'll need to start with adding some basic layers; Metal, Rivets, Fasteners,Weathering,and Paint. Not necessarily in that order though. Typically you'd do metal, paint, rivets, fasteners, and weathering. Just really depends on how you want the skin to look.
Now this is something I do and maybe others do it too. I outline the major body selections. I'll even outline the individual components that I may not even be changing. Use your marquee tool or lasso and try to be as precise as possible and trace the area you want to save. Once you've got it outlined with the marquee/lasso tool you want to save it to a alpha channel. What this will allow you to do is quickly grab certain areas without affecting everything else around that particular layer. I do this with every selection and name them accordingly so they are easy to reselect.
Now start with your basics. First and foremost your panel lines and basic metal layer. Select your panel layer and use the pencil or line tool to draw over the already existing panel lines that HT has done on their skin. So long as your on your panel line layer you don't have to worry about altering the original picture. Typically you'll want your panel lines 1 pixel wide. If you have a pen tool it can do wonders for panel lines. Now trace all your panel lines and your done with that for now.
Keep doing the same thing for each layer until you've got a basic setup. I myself prefer to do all the metal, rivets, panel lines, fasteners and sometimes the basic weathering first. Then I move on to specific paint schemes, weathering, tint layers, ect... Hopefully this will get you started. Be sure to check your picture size, it should be 1024x1024 in resolution. You want to paint in RGB and then when your done change it to a indexed photo for implementation into the game. I'd suggest though when you feel you've got a decent initial setup. Do a copy merged layers and paste it to a new file with 1024x1024 properties. Then save it with the correct game file names. Then when your done editing for the day you can save your original "template" as a PSP or PSD file so all your layers will still be there when you go to open it up again later. Hope this helps some.
