Wow, this is a tough one. Will there be any heat source in the garage like a wood stove? Not sure how much that would help, but it would help some at least.
I would try not to compact the pieces together and keep the wood away from the fabric. As much as you can keep it all uncompressed, the better.
A dehumidifier might help, but it depends on the garage.
What part of the world/country are you doing this in? What's the climate?
I am not sure what drying agents you could use. Some may say rice, but I fear that would hold
close to the materials and perhaps invite critters.
Definitely should be an interesting thread though. Can't wait to see what Bob and Heirony have to say on this one.