I am by far no expert on this topic, but I would say that if the wool is already felted when you buy it, you do not need to re-felt it.If you are using woolfelt, then you need to wash it first to felt it. I am making messenger bags for DGD's with wool from recycled 100% wool plaid skirts. I did wash them to felt them. I think you could probably use glue stick to hold the pieces in place, or I use the small stick pins and they work well. I wouldn't wash it after it's completed. you can use freezer paper to make your templates for cutting out the appliques,