I use a simple home made crown molding jig when I have a lot of repetative cuts to make.
I have 18 window sills that get crown under the sill, so I had a zillion return ends to make.
Back board gives you a place to line up your pencil marks, without eyeballing your mark to the blade every time.
Base board keeps the crown in position for every cut.
I usually cut all my crown upside down.