Oh chickens can get wet, they just don't necessarily care for it.
Not sure if the chinchilla dust is ok for chickens but I don't see any harm in testing it out and seeing if they like it or not. Might need to be mixed in with heavier matter so it doesn't just go flying everywhere
OMG, I bought that same product, It wasn't cheap, chickens didn't use it!! I thought that during winter they wanted to dust bathe, hard to do with FROZEN Earth and SNOW, They like DIRT better... it was a WASTE of my money.