Welcome to my tutorial on the basics for learning to skin for a HL1 game. This tutorial will explain getting the skin to actually work. This tutorial does not explain the actual skin editing itself, just everything that needs to be done.
A decent photo editing application. I will be using Gimp 2.4 today.
Jed's Half life model viewer, found Here. Ill be calling it HLMV.
GCFScape Found Here.
A basic knowledge of image editing.
Open GCFscape and open the desired game .gcf. I will be opening Hal life.gcf.
Go to Valve/Models to find all the .mdl (or model) files. When the desired model is found, drag and drop it to your desktop. For the purpose of this tutorial, i will be using v_grenade.mdl.
Click the Textures tab at the bottom, and pick the texture you would like to edit.
Click Export texture and save it as the same name as shown. In this case, it is grenade3 and is in .bmp format.
Open this file up, and the image will be indexed. Go to Image/Mode/RGB. This will give more editing options.
Edit the file how you wish.
When done editing, go to Image/Mode/Indexed. if this step is not followed, the texture will not import in HLMV.
When the image is indexed, save it as the name it was originally given, in .bmp.
Open the model back in HLMV, and go to Import texture. If everything was done correctly, you will see your edited skin on the model.
Now, go to File/Save model as and save it as the same name it originally was. In this case it is v_grenade.
Place the .mdl file in the same directory that was in GCFScape. In this case, it would be Half life/Valve/Models. If done correctly, your skin should appear in-game.
Here is an example.