Another alternative which I use along with the double bag liner, are those space saver bags you see advertised on info-mercials. Most outdoor places carry them.
There the kind you seal the end and roll up, where a one way valve purges the air out. Waterproof, bug proof, and really compresses your load. I put one outfit, shirt/pants/socks in a medium bag, and use other medium bags for extra socks/t-shirts and fleece outerwear.
I stack them in a mesh duffel type bag which I take in tent at night.
I use them for dirty laundry as well.
Much better than zip-lock bags and easier to keep track of your items, and get all the air out of.
Coleman makes them, I'm sure there are other brands on the market.
Last set I got was at Bass Pro Shop.
Between liner bags and these, your stuff will stay dry and easy to find!