When I lived in Tx I constantly fought low humidity for drying. I ended up with a small cold air humidifier with a variable rate and it worked perfect. I'd normally have two hydrometers one set up low, about the height of the lowest hanging buds and one up near the lines I used to hang the branches.
I had a 5'x8' walk-in closet and used a small 8" fan on low to indirectly circulate the air.