To do this, you need stuff sacks. But not just any stuff sack. Most stuff sacks are made from woven nylon or silnylon which can absorb water. Silnylon is only woven lightweight nylon that has a silicone coating. There are no standards set for the thickness of this silicone coating, and there is a lot of variation in quality between different manufacturers.
To keep your essentials dry and your pack light, I highly recommend Dyneema® Composite Fabrics (DCF) bags – Formerly known as cuben fiber. DCF is one of the strongest fibers in the world, laminated with a waterproof plastic film, and is much lighter than nylon or silnylon. I like to keep my sleeping bag in a roll-top stuff sack. I use a roll top because after I stuff my sleeping bag into the stuff sack, I can kneel or sit on it to remove the excess air still trapped in the sleeping bag. I’ll quickly close the roll top and end up with a much smaller package to put into my pack. Little tricks like this make a big difference as the more you can compress your sleeping bag the smaller pack you might need or the more food you can carry.
If you're looking for awesome hand made and custom DCF gear ranging from stuff sacks to a range of different bags / backpacks among other neat things visit Eva's shop at https://bit.ly/2S6o8mr. You need something specific that you can't find anywhere? She will build it for you.