250 acres is alot of posted signs but,,,you gotta post it. Than on the first couple of days of all hunting seasons,[bow/gun for deer,,,squirrel,turkey],,you gotta be out there patroling your property,,,you could just act like you were hunting too,,,once you let them know where the boundries are and you are there watching,,they will get the message.
Another thought is you said you let one guy hunt,,,if you don't want to deal with it much,,if you could find one or two guys who loved to hunt but were safe and could be trusted to not bring in any more people,maybe who didn't have any land themselfs,,,maybe let them take charge of it during hunting season,,they would protect your land from others,,,trouble is finding a couple guys like that.
In w.va.,people have to have written permission to hunt on posted lands,so you could write just those two a little note.
Yeah,the main problem you got is your property borders state,[or tva] property. A lot of people who have been run off other private places for good reason, hunt these kind of areas,,very dangerous. thingy