Ok, the title contradicts itself because skinning is not basic. It takes time, patience, and skill. Get used to it.
Now, I come over here about once a month and typically I see some so-so skins that make me think "meh". However, it has occurred to me that there are not all that many examples for people to follow, and thus, here is a short skinning tutorial.
So, I see this skin made by tntsomerandomnumber:
Now, there is nothing wrong with this skin. Until you say it's done. This is the START of a skin, the very tippy top of the ice berg. Rule number one for all game art (or for that matter, all art): Have three levels of the image: Base, blocking, and detail. This is the minimum for a realistic/detailed skin. Each one has to be done separately. There are very few shortcuts, and it is normally easier anyway.
First off, lets finish off this base. If you are lucky enough to have photoshop, it will be easy for you to follow along with this. Select the "burn" tool in the toolbar (a hand), and brun around most of the sides and such. Use exposure for the sides around 17%, and for the middle, around 40%. The image below shows what I did:
Knowing this, what can we use for blocking on this skin? Well, it kinda looks like metal, so lets start there. Perhaps some construction equipment? Sure, lets add some yellow highlights around the tank. Make a new layer. Take the basic brush at about 9 pixels, full hardness (heh), and draw lines around the basic corners on the tank. Hold "shift" while drawing if you want 90° lines; click, press shift, and click somewhere else for a line between those two points; or just do it free hand if you really want. The former two options typically look the best. Now, look in the layers palette (shows the layers) and go up to a scroll menu that says "normal". Scroll this down to "Overlay". I know, it now looks awesome.
Sadly, this is an awesome vehicle that has been through hell, so painting won't really be pristine. Let's roughen it up a little. There is a more professional way to do this using masks, but for now, lets just use the eraser tool. Select it, and set the brush to be something that looks bumpy and uneven. Good choices are in the Faux Finish and Natural Brushes 1, 2. Set the opacity (along the top toolbar) to 45. Now roughen up the edges on the yellow paint layer.
COOL! Remember that third layer of detail I talked about, though? Time for that. Make a new layer under the yellow layer. Spill-paint this layer with a medium gray (middle between black and white). Select the burn tool, set the size to three pixels, set the intensity to 50%, go crazy. No, really, hold down the mouse button, and wave it around like you just discovered... awesomeness. Get a bunch of random zigzags going all across the screen. Make sure you get an even coat after about thirty seconds of this, and then bring the size down to two pixels. Repeat, only change it to one pixel. After you have the three levels added of the burns, go to where we changed the yellow to "overlay" but instead change this to "Multiply." This will instantly make everything in your image darker, but if you give your eye a chance to adjust, you will see how awesome it looks now.
Ok, one final touch. In the same spot that the burn tool is, there should be a tool labeled "dodge." Select this, the exposure set to 40%, and with only the two pixel normal brush selected, go crazy around the front of the turret, the fronts of the bumpers, and a couple other places where you think it will look good. After you have done this, add little tiny nicks and scratches all across the board by making both long random strokes and calculated short strokes that you move back and forth. The result, a realistic looking metal texture. The dodge adds a very subtle, but necessary, detail that attracts the eye just enough to trick it into realism.
The last step that I'm going to do is completely optional, but I think it makes it look much cooler. Select the sharped tool (tall triangle), set the size to 200 pixels, and click once or twice over each part of the crazy layer. The outcome makes the scratches look like they actually have depth, and an overall badass texture:
Once again, though, please don't consider this done. You still need to make a gun, add wheels, and probably a couple more yellow lines at least. Do some more detailing with the burn and dodge tools, and for gods sake, stay away from filters. Good luck!
