There are as many ways to do this as there are people doing it. Generally, I drop the origonal bag and use a Granite Gear compression sack. It has three options.
1) Normal Bag in a bag.
2) Two sleeping bags: For the wife and myself. I usually carry this.
3) Solo: With additional long johns, long & heavy wool sleep socks, and down jacket.
The biggest failures of the WM bags are the tiny sizes of their stuff bags. Breaking camp in the morning is always a chore when I was using the factory supplied bags. That's all right; it is the smallest they recommend for stuffing the sleeping bag. The tiny bags also take a few minutes to work the sleeping bag into, though. I don't think I ever did this without working at it. A larger bag helps a LOT when breaking camp and, un-stuffing at night. The sleeping bag does not need the extra shaking and lofting necessary when the bag was heavily compressed. This can take about 10-15 minutes for a heavily compressed bag. Using a one size larger bag will reduce this to 2-5 minutes.
Hmmm...a little explanation....
Generally, I take a bag that is lighter than recommended. Usually around 1#11 for down to around 20-25F. Since I need a jacket after hiking anyway, I simply add this into my stuff sack. Same for sleeping cloths. In a pinch, say a 25F morning, I have all the layers on, but they are NOT needed when hiking. The jacket weighs about 11 3/8 oz. The pants weigh about 5-8 ounces(light or medium weight.) And the shirt weighs around 10-14ounces (again, light and medium weights.) Basically this lets me use one bag from around mid spring to October/November (depending on the year.) The sleeping cloths pick up body oils rather than putting them into the bag for the first week or so, and, adds a bit of longevity to the bag on longer two and three week trips. Anyway, look for a stuff sack around 5-6" dia. It should *just* fit into the bottom of your bag when you are done putting your sleeping bag & sleeping cloths in it. Don't compress it beyond the size of the pack. It will add a little rigidity to the overall pack. And, it should be about the same diameter as the pack is thick...usually between 5-7". A dry bag is good for wet weather but it also weighs more. When stuffed it should be fairly soft to fill in the corners pretty well. I use a small volume pack (~2800ci) most often. Soo volume is fairly important. Bushwacking or off trail travel wants a smaller pack to keep snags to a minimum. Same for scrambling the High Peaks area in the ADK's. Using a stuff sack (or dry bag while canoeing) lets me keep things quite small. It will also keep your bag dryer in the event of a spill or heavy rain storm. The compressed bag will not be quick to pick up tons of water. Down works well even damp. (Synthetics should NEVER be compressed, so I'm not considering this.)
Generally this is about the whole sleep *system* you will use. The tiny bags supplied by WM are really too small to be convenient. (But, you *can* dip them in a bucket of water and not soak the whole bag. High compression means your bag will resist water penetration.) Getting a larger stuff sack has several benefits for the additional 2-3 ounces in weight, but may not work well for you. Not using the stuff sack is NOT recommended except for dry areas. A dry/compression bag works well for very wet conditions. Note that down can be compressed a lot, as evidenced by the small stuff sacks offered by WM, without damage. The more you compress down, the more time it will take to uncompress it at night (sort'a increasing geometricaly with higher compression values.) It is ceartainly possible to use additional clothing to extend a bag's temp rating, but all(sleeping bag & sleeping cloths) needs to be kept dry so as not to introduce moisture into the sleep system. A stuff sack can add rigidity to your pack, making it easier to carry without fold up.
My thoughts only . . .