You are right. There is no Cursors.Default static property. But you can always set cursor of a control to null and it will restore control's default cursor.
// ...btn.Cursor = Cursors.Wait;// whatever... your operation.btn.Cursor = null;// now the Cursor is default again.
I think you need to store the current cursor in a variable before changing it to the Wait cursor and then set it to your cursor variable when you want to change it back.