Modview

It's quite ez to use ^^ :

1) go in assets0.pk3, and take the folder "_humanoid" located in models/players/
extract it to gamedata/base/models/players/ folder

2) Download modview, and etract the modview.exe to your desktop. Now launch it.
now, go on file/open, here get the path to your model.glm of your skin, then open it.

**** TO WORK, THE _HUMANOID FOLDER MUST BE IN THE SAME FOLDER AS YOUR SKIN FOLDER !!! ****
<img src="https://2img.net/r/ihimizer/img444/4769/modview.jpg">

In the tool : to change point of view : mouse left click, then drag.
to change fov : mouse right click, and drag.

each time you edit a texture, save it, then refresh your model : it's the third icon starting from right at the top.