DIYGuy! You only need to do the walls that lead to the outside so that's usually only 1 or 2 walls in a room and not all four. It looks great. I put it in matt paint. It has a very slightly sandy texture when dry, but is not noticeably different than walls painted without it. It takes a while to mix it in, but is no different to paint than regular paint. You can use a brush or roller. It dries quickly. I actually felt less cold coming from the wall after the first coat before it was fully dry. I really like this stuff.