It kinda sounded like someone was putting you on!
The Recreational Vehicle places sell desicant kits.
One thing that really helps is heat, which you have, and air circulation.
My buddy has a garage where the floor would get wet in the winter. He started leaving the garage door open a crack and opened the window on the opposite side a little. The floor stays dry now. Just that little air movement was a big difference.
The other thing is if there is any way you can leave your car out where it can dry before bringing it inside the garage.
I think the moisture you bring in is what you should try to reduce.
If you had moisture on the cement floor, I could see how spreading kitty litter on the floor would draw it up and expose it to the air for drying.
The worst place to leave a car is in a car trailer with any kind of leaky roof.
I had a new enclosed trailer and it had a small roof leak which caused a sauna like effect when the water evaporated during the sunny day, but condensed on the cold metal parts of the car at night.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer