Here's a map of one layout I played with 18 disc golf holes on 9 golf holes. You basically follow the same routing, though the disc golf holes often tee off in front of the ball golf tees, and our holes are shorter overall. There is one tee and one pin on each side of the fairway, offering 4 different 9 hole layouts and 36 different shots overall. I thought it worked fairly well, the flow was pretty good with longer walks for disc golfers but slightly quicker play.
The yellow dots are disc golf tees, the red dots are baskets: