my rule of thumb is, if its a close friend and you are already mid conversation on the way in, you can keep talking as long as you keep looking "straight" (pun intended). If one of you arrives while the other is mid-stream, i generally avoid the greeting and minimize responses, and grunt during the silence to deter the other from the urge to start. Now that im old, it takes me a few minutes to start, so that can be awkward too..if there is no pee sound coming out, why the hell are you here? 😆