Shad darts work well and yes, many times the take will be on the fall. Shad darts are very easy to tie. Take a size 2 salt water hook and tie on a small amount of marabou for a tail about 3/4" long, wrap shank with silver or gold mylar, tie on a medium heavy dumbbell and wrap Estaz chenille around dumbbell. Done. I tie mine in all one color in white, red, orange, chartreuse and pink. If you can see the shad and they are not responding to your fly, change colors.
The whole key to shad is finding them. They move in tight schools right along the bottom and where you find them today they might not be tomorrow. The Delaware is a large body of water and the shad follow specific currents so don't expect to show up and find them everywhere. If you can find them they can be caught but finding them is the key.