It's actually low humidity that promotes static build-up. High humidity tends to bleed charges down like the anti-stat chemicals do. Same reason: ions conduct electricity, and moisture tends to ionize things because water is highly polar.
You can buy an anti-static mat made of conductive plastic and that you ground to a water pipe, and work on that if the problem is severe. Most find the clothes dryer sheets alone are adequate, but leaving detergent on something has the same effect. It tends to attract enough moisture to remain ionized. You can buy a cheap anti-stat wrist strap
and ground its wire and put it in a powder hopper or around the metallic parts of your press. These just offer a high resistance path to ground that bleeds static charges off without allowing current to get high enough to cause a hot spark. It's not easy to get one hot enough to light powder, so it's more about precaution and "just in case" to use the high resistance ground path. It certainly stops a spark from being painful. You can wear one of these straps, too, to help stop static on your body from affecting scale readings.