I avoid needing to adjust the size of textures I create by making them the right size to begin with. I draw a rectangle with at least one dimension matching a known dimension in the texture. Then I import the image as a texture and apply it to the rectangle. Starting in the lower left corner of the rectangle, I drag the material out and click on the far edge at the known distance. For example, if I have a wood grain texture that is 12 feet long, I make a rectangle that is 12 feet long. The width can be whatever because the texture takes care of that automatically.
Usually when I am making wood grain textures, I make 3 or more of the same species from the same log. I just make as many rectangles as I have texture images.
Inspecting mirrors is a job I could easily see myself doing.
If you are the smartest person in the room, you are in the wrong room.