If you can brush every inch of the pool and the water stays clear, you pass the OCLT, and the CC is less than .5, you're done. There should be no visible algae anywhere, not even lurking on the grout lines inside the skimmer throat.
If you're unsure, keep FC up at shock level for another day. If the algae is truly gone, you won't be losing much and it's really cheap insurance. What's another jug or two compared to 20 or 30 to SLAM it again?