I live in Oregon City, so Clackamette Park is a convenient access point for me. There's a short stretch just in front of the Rivershore Motel that is far enough away from other anglers that I can usually work in there with a fly. I use a high-density shooting head to get down. There's no real room for a backcast there, but the shad are within 30 feet of the bank, so you don't need to cast much farther than that.
I used to find shad in the Clackamas in the big, slow pools in the lower river. Some of my favorite places have filled in, and I need to find some new areas on this river. I'm sure the shad are there, but haven't been able to score yet.
Bradford Island, at Bonneville, used to be a notorious shad fly-fishing venue. Again, don't know anything about it, recently.
Obviously, I need to go fishing more.