Mark,
I don't know about the wet sock... I'd be afraid it would stick to the skin when it freezes... those rainbows have delicate skin. I could be wrong though. I just wrap the fish in 3 or 4 garbage bags. When are you planning on bringing it to the taxidermist?
I prefer skin mounts. I think they look more real. The only problem is that with a rainbow there is alot of painting involved. It is really hard to get the exact colors... even with a photo. Make sure you get an excellent taxidermist for your trout. Trout & Salmon are an entire different ball game than bass & pike... Alot harder!

let us know how you make out.