I am by no means an expert, but I'll try.
If you're using 3ds max like I can help.
You're going to want texporter get it here (
http://www.cuneytozdas.com/software/#texporter).
install it.
ok now, say your model consist of one cylinder. There are several ways to tackle this texturing job. all the ways I know start with
UVW map, what this does is determin how the texture wraps or is placed on the mesh(note if you want the inside to be diffrent than
the outside you should detatch it and 'wrap' it seperately). After you map it go to the utilities(the hammer) and click more and
chose texporter, change the image sixe to be square(I usually use 1024x1024) and click on your object. the object should almost
fill the texture, thats ok we just used this as a easy way to make the base skin, save this and what ever the texture is suppose to
be.
Now what we're goin to do is adjust the size of the area this texture takes up. Open the material editor. On the right side of
diffuse there's a little box, left-click and a list pops up. click bit map and chose your texture. click the checked box so it
shows in viewportthen with ony the part you're texturing at the moment selected, click assign which is third from left on the same
tool bar.
you should see you're texture wraped on the cylinder.now select Unwrap UVW from the modify list and click edit. you should
see a flattened wire frame of you're model layed out, reposition this and resize it so that you have room for everything else you
need to texture from this model. Once you're happy with the results go back to texporterclick pick object again and click on the item,
it should produce a new texture that reflects the current mapping, since this is the first texture you can just save over the
original texture, for later additions save the new texture as a file named temp.bmp or something and open it in photoshop, once in
photoshop have the temp file and the main texture open right-click on the layer and duplicate it into the main texture and change the layer option to lighten.
Ok, I'm going to quit now, if this didn't help or if this was just useless crap, just ask me a specific question and I'll try to anwser it better.