Gently, slightly taping the mouse button, when applying textures, you can create a subtle overlay, a hodge-podge of different mottled textures, and you can copy and paste that custom mottled texture anywhere you want it.
BTW, I keep one spare baseboard, off o the side, where I keep a "painters pallet" of all my favorite textures, so I can easily select them, rather than searching for them. As with all my favorite assets: trees, buildings, tracks, signals, signs, locos and cars...I also have them off to the side, on my one basebord "painters pallet".