The trick to getting the meatloaf out in one piece is to line the slow cooker with a layer or two of foil, then use the foil like a handle to lift the cooked meatloaf right out.
Line the insert of a slow cooker with two 18-inch long strips of foil crossing over in a “T” shape. Allow foil to come up sides of the insert but not above the lid line. Coat the foil generously with cooking spray.
Finely chop the mushrooms in a food processor (or chop them by hand). Transfer to a large bowl. Add the breadcrumbs, paprika, and salt and mix to combine. Add the egg and turkey and gently knead to incorporate. Transfer the meat mixture to the prepared slow cooker, pressing out to the edge of the insert and mounding slightly into a domed loaf shape. Cover and cook for 4 hours on the low setting. Unplug the slow cooker.
Remove the lid and top the meatloaf with the barbecue sauce. Allow the meatloaf to cool about 20 minutes before removing from the slow cooker using the foil as handles.