Don't make the same mistake I did!
I picked up a small (margerine sized) tub of dissicant at the local hardware store. I had used it in my gun safe when I lived in North Carolina.
Then I got a bright idea.
Put some of the stuff in a sock and tied the end off.
Put the sock in a foam lined rifle case.
Put my AK 47 in the case and headed to the range. Did the same with a Winchester Model 94 that was new.
Left the cases in the car in the sun for about a half hour while I looked at stuff in the range store.
Went to the range, opened the case and the dissicant had melted and was quite caustic.
Ruined the finish on the AK. Rusted the hell out of it. Ruined a spot on a new Winchester Model 94. Rusted right through the blue.
I had to send the AK off to shootinirons to get it refinished.
Unless you store your guns in the cases or keep them in the cases for extended periods of time they are not likely to rust in a few hours.
I don't know how the medicine bottle or camera case little packs of dissicant work or if they will melt. But the hardware store stuff that comes in a small tub will wreak havoc with your weapons if it gets hot and melts