so, as you know, the humidity needs to go up. lots of people use a spray bottle. depending how low the humidity is where you live another option would be the sock trick. Take a long clean sock, soak the bottom 50% of the sock with warm water, fold the sock back up into its self (like you do with a pair of socks you are putting away), place that over the heat source. I like this option because it slowly increases the humidity rather that spiking it. Its also nice for the low humidity areas because you wont have to spray 10 times a day.

depending how bad the humidity is where you live it may be worth switching to a different substrate that holds moisture better. Good luck