When I leave kiel I only have a seaman on watch and my other guys can just rest especially in the type II because it saves endurance. When I get near enemy territory I put my WO on the bridge and fill it with crew. I have found the WO gives u the bearing and ship spotted and if he is not on the deck you will get the shiskavesha
sound ( cannot pronounce the german ) but if your in time compression I believe you will not get any notification.