I do have a wool comforter - haven't had cause to wash it yet (and I don't recall whether it's machine washable or not. . . I should doublecheck that actually before winter) but my loose plans are to handwash it in my bathtub on a day that I can dry it outdoors. I also have some not-machine-washable wool pillows, and I've spot-washed those before with a gentle liquid detergent, and left to dry outdoors (which is good regardless for the wool whether you've washed it or not - to sun it outdoors regularly, it's said that it helps it re-fluff up too).
I do know that the wool they use it the machine washable pillows or duvets is different than the non-machine-washable ones (though I don't remember enough to tell you how in detail), such that it's less likely to felt up with the agitation of a gentle or handwash cycle in your machine. And either way, it's also different then the variety of kinds of wool that you see used for diapering too.
I'd be pretty apprehensive of putting it in the dryer at all. I'd also try to make sure to use a washing machine without a central agitator. And I'd use a gentle liquid detergent (can't remember if woolite is okay, but it likely is, I use liquid charlie's and also have kookaburra wool wash which I'd also use on my wool bedding items).
We have Natura wool comforters. I have washed them several times and they are fine. I do them in a front-loader with Kookaburra wool wash, then tumble dry without heat until mostly dry, then finish in sunshine.
There are 2 sorts of wool duvets on the market in the UK 1) machine washable and 2) dry clean only. The washing/dry cleaning instructions will be clearly marked on the duvet.
Bear in mind to get wool machine washable it is put through a number of chemical processes - either chlorination or the application of a silicon residue which alters the fibres in the wool and prevents them from felting if wet. Dry clean only wool duvets have not been put through these chemcial processes - hence their attraction for people with sensitivity/allergies to these chemcials or people wanting something as natural and pure as possible.
In the absence of any spills or accidents, it should not be necessary to wash or dry clean a pure wool duvet on a regular basis. Wool "breathes" and so stays fresh. All you need to do is air your duvet every week when you change bed linen.
I know a lot about wool duvets - I sleep under one (take it away with me when I travel I am so attached to it!) so feel free to come back to me if you have further questions - will glad to help.
I have one and I machine wash and dry it with no problem. Its instruction says it's OK. I didn't like it very much though as it's not as soft as down filled ones. So I mostly use down comforter now.
I have some holy lamb mattress toppers that are machine washable and they send instructions with it. You are supposed to put it in the washer and soak then spin. Do not agitate because that will cause it to shrink. Then rinse and spin again. I have washed mine and no shrinkage at all. I accidently let my daughters go to agitate and it definitely shrunk.
Look at the care label on the cover to see if it can be washed at home. If it says "Dry Clean Only", then take it to the drycleaner; otherwise you can wash it using the same technique you used to wash the duvet. When both parts are clean and dry, reassemble the duvet "sandwich", close the edges and make the bed.http://www.treathemorrhoidsguide.com/