Misting during shedding should bring the humidity up, just once of twice a day.
I would suggest getting an Acu-Rite digital thermometer/humidity gauge. You can probably pick them up at Walmart. I got mine at Lowe's but I don't know if you have one there.
If you're really concerned...I have a Ball Python and the humidity was VERY low for him, in the 30's. What you can do is place a damp towl on 1/2 the tank lid. But that poses a problem if you have a heat lamp. ((Heat lamps SUCK mostiure out of the air and IMO you don't really need one, just a good UTH)).
But what I did to sole my humidity problem, I threw away the mesh tank lid I had and went to a hardware store, got a 20x10 piece of plexiglass and cut two holes in the top using a whole saw then got some mesh wire to cover up the holes. I drilled 4 holes around each big hole and inserted 4 screws to hold the mesh in place, works like a dream!
But with the method mentioned above, you cannot use a heat lamp.