Do you just guys put your models together before you take them apart to paint them, or do you paint them out of the box after you cut/sandpaper/etc. the parts?
That depends on the modeler and the kit itself. Some like to put the kit together to get a good feel of it and make it easier to paint though with some kits that might make things too difficult as taking it apart might be risky or not possible at all.
Of course I've never painted a kit, at least not successfully.