Put a grid over your search area and share one link. Everyone out looking can see which ground has already been covered — and, more importantly, which hasn't.
Takes about a minute. You get a shareable link at the end.
Post it wherever people are already talking — the neighbourhood group, a text thread. Searchers need no account and nothing to install.
Blocks turn blue when someone claims one and green once it's covered, so two people never walk the same ditch while a whole field goes untouched.
Green fades as the days pass. A pet moves, so ground covered on Monday is worth walking again by Thursday — the map keeps saying so.