David,

You can put your zipped up (breathable?) rain parka over the foot of your bag to keep it dry if it touches the tent wall.

The best DWR I've found is REVIVEX, a spray-on DWR used by Gore Tex garment manufacturers. I use it on my down bag. Two coats works best. Tectron DWR is the next best. I've purchased both at my local REI store.

Do NOT use the Nikwax "wash-in" down water resistant stuff, even the one labeled as made for down water repellancy. Reports are that it makes your down loose its loft. Down has the natural oils from the gooseto help it repel moisture. To retain these oils use only the products specifically labeled as "down wash" products. Never was down garments with detergents.

Eric
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"There are no comfortable backpacks. Some are just less uncomfortable than others."