I have done a proper skybox, inserted a skyportal in it, wrote a shader for it (actually copied it), (It is a stratisphere skybox). But I dont know what texture to use on the walls of the actual map (and not skybox). Do I leave them caulked, or some specific texture? I have read guides, but thye dont say what exact texture I need to use
Thank you for the help!.
skybox problem
Use any functional sky texture - I usually use the goldrush sky.
Make sure that you perform a full vis, using “vis -fast” can give you the HOM effect.
Do you have to have a light inside the skybox? Because everything I am getting is just black walls.
Are there any lights in your map?
The skybox shader should emit some light but because it is a night sky you may need to brighten the map up a bit.
You could always put “_minlight” “15” in your worldspawn entity until you get things lit up properly.
I dont have any outside light at all. The only light is from the sky entity.
Is it possible to have a full brightness texture without the light? Do I need to do in the shader, or put light into the skybox, or actually light the walls of the map? Thank you for your help! 
Oh, light in the skybox worked, thank you!. The very-last question, how to mirror a texture? Not rotate by 180, but mirror it 
Ok, I have done a good, working skybox, thank you for all your help!.
And just wondering, is it possible to use movers in the skybox? Because I have tried a func_rotating with origin and spawnflags 1, and it just didnt appear in the map…
I have seen skyboxes used with animated shaders (blinking lights on a tower), never one with something physically moving in the sky portal cube.
Why, you want to create a moving sun? 
My suggestion for that is to create a sphere al around the map.
So there is kind of a platform in the sphere, and let the sphere turn, keeping the map itself horizontal
I know, from the lot of experiments that I did yesterday I found this :
- It is not possible to use mover in the skybox. It will not just be transferred as a sky part
- It is theoretically possible to change the angle of the skyportal, but the script for that will not provide a smooth rotating and will delay all other scripts.
So, generally speaking, skybox is only for static skybox, therefore if you want a moving sky, use a mover in the map with a shader, which will provide an effect of the sky light.
And i is not nessesary to make it a sphere, just a cube is enough.
And I need a rotating sky for interactive gameplay, because I have a space-ctf map, with a lot of space visible, so moving skybox will give an impression of the buildings themselves rotating in the space…