These are the steps I followed to clean up our mattress, and it took hours but it worked! The mattress smells 100% clean and there is no stain at all – which was a big relief because our mattress is only a few months old!
In between all these steps, the bedding was loaded into the washing machine, and I cleaned the goose down duvet following the same steps as for the mattress, except that I did it all in the bath tub, which made it easier to wash and rinse. (Being a Super King size, it would not fit in our washing machine).
I moved our Dry Soon heated clothes rail into our bedroom to hang up the duvet, so it would be near the dehumidifer. To further speed up the drying process, I used the dog blaster on Hot to help dry both the mattress and the duvet.