Tips and help to skin?

I’m doing at moment an FDF project to Garry’s Mod and my plan was to do these:

Modern army, tanks, planes= ragdolls, S-Car maybe, WAC maybe, playermodels, NPC maybe
Cold war army, tanks and planes= Same
Rk62 swep=WIP
And i maybe try to make finnish WW2 skins too

But i’m in kinda problem. I haven’t really made skins to Garry’s Mod or to any Source mods/games. So i’m asking some tips and help for skin making like:

What tools i should use?
What programs i should use?
How to hold the post in good quality?
How to get camoflage in better quality?

Also i’m really interested about simkas models and ragdolls. They are awesome. Professor Heavy aswell, And i would be happy if i could use them to make this

Feel free to give tips and help, i try to make the best of me :smile: