I'd try for unscented wax. I've also heard that Nu-Skin, stuff you can buy for wounds from a pharmacy, works really well. If you don't have those I'd try the medical tape like WV suggested, and if you don't have that, scotch tape

I've successfully done scotch tape before.
Humidity is hard to say. I personally use a lower humidity, around 30%, but that won't work for everyone. You kinda just have to figure out what humidity is going to work best for your area through trial and error. You might want to lower it to around 40% and see how that's working by watching the air cell growth, and then adjust as needed.