This is normally unimproved overcards. The only overpairs that slowplay are AA and sometimes KK. Everything else is vulnerable. If he just smooth called your flop bet he is telling you he doesn't have an overpair. bet HUGE on the turn to blow his odd socks off. If you get called there, then slow down to a halt. After all, it's not impossible that he has an overpair. It's just unlikely.

The answer is to bet until he gives you a reason not to, just as rilla said.