There are spots along Donegal Creek road - just don't block any gates or wander too far into planted fields with a vehicle. You can also park along route 772 and walk downstream to the top of the FFO. I think there MAY be signs on some of the farm lanes stating "fishing permitted, walk-in only" but I could be running different streams together.
Just fished the stream yesterday, didn't have too much time there, so only got to explore a short stretch but I turned up fish throughout the portion I was fishing. We parked along Donegal Creek Road fairly close to the intersection with Long Lane.