There are some good tips there, but I have a couple of points:
You'd cut down on brush count if you used two 4 sided pyramids, aligned by sides, with each apex chopped off by a cuboid (or just use one cuboid if the texture alignment allows for it).
I tend to make door frames by having one solid brush going all the way through the wall, with the doorway itself cutting though it. If the frame is to stick out, I can also make the airbrush bigger. That only works when the frame texture has no obvious direction and when the floor texture is the same from one side of the doorway to the other.