PG (Propolyne Glycol) is often used for humidification. It's not the best choice and it's not the worst but it's not great...
It's pretty easy to season your humidor yourself with a sponge dampened with distilled water. Total cost < $2.00 and it usually takes a week or two. Save your money and do it yourself. There are lots of threads here on CA that can provide detailed instructions. You can start here:
http://www.cigarasylum.com/vb/showthread.php?t=620.
If someone says that they can season a humidor for you in less time, take your business elsewhere...
Once your humidor is seasoned you have a lot of choices for humidification. I am biased and recommend beads (Heartfelt (
http://www.heartfeltindustries.com/) or
HCM (
www.hcmcigarbeads.com).