Paint on UV'ed model with external editor The thing is that the guide I'm following uses 3Dcoat to have the texture projected from the one side to the other side. I figured that Blender would be able to do this also, but I'm not quite sure how it works. I've tried to search the internet and there's probably guide, but I do really not know what to search for to find what I'm looking for.

Guide that I'm following: https://www.youtube.com/watch?v=FiNASmArkxA

EDIT

Thanks for the help, I found what I was looking for. https://www.youtube.com/watch?v=hb-OZTNFatw
UV unwap the object, enter edit mode, go to the UV editor, click UVs at the bottom and finally click Export UV layout. It will give you an image with a UV template image, which you can paint over and then load back into blender.

Update: Based on your comment, try cutting the object in half using K and deleted one half. Then use the mirror modifier to restore the other side. Then position the viewport in the position you would like the final 2D texture coordinates to be. Now go into edit mode, press U and then unwrap from view. Follow the remainder of my steps from there.