You need to already be familiar with photoshop and source skins. Works only on Deafault models!
First download vtfedit (Valve Texture Edit) here http://www.fpsbanana.com/tools/95
Okay now download a Source skin were going use this Deagle by reaper
http://www.fpsbanana.com/skins/932
Once you have downloaded and installed "VTFEdit" go to properties and set "always open with" then find vtfedit and double click it for source VTF files only.
Now double click the VTFedit skin you see, then export it as a .bmp. Go to File then export make it a bmp.
Now open the .bmp with any photoediting program and decrease the color depth by 16.
*You can use Adobe Photoshop but you need to make it an Indexed color so
go to 'Image' 'Mode' then click on the Indexed Color. (There will be a prompt simply press 'Enter' do not mess with any settings) This also makes it Portable to JHLMV Jeds Half Life Model Viewer.
Now resize the skin if you have to and your done.
*Photoshop 'Image' 'Image Size' set the Pixels to what they need to be in JHLMV. Like usually 1024x768
Open Jeds half life model viewer and import the source texture that you edited.
If you don't get it, Private Message me and I'll help you as best as I can.
You're basically just opening a picture in a different program and then exporting it as a extension you're (CZ/CS 1.6) familiar with and decreasing its color depth.
This is for your own personal use. Do not upload to FPSB as it is illegal to do so.