Duffel Bag Liner – Gear on Kilimanjaro
Just like your day pack, you can use plastic bags to line the inside of your duffel bag. Even if you have a waterproof duffel bag, you should create another waterproof lining to help combat the rain and elements.
I had a waterproof duffel, plastic bag linings, my clothes in individual plastic bags, and moisture and dirt still managed to slip in.