I think you shouldn't take these specific rules as a general advise. Don't use your hands directly untill you are sure your hands clean. Even most Japanese don't do that. And a rules imposed by a restaurant may be acceptable but a rules imposed by you to your acompanies are often uncomfortable. Japanese calls such kind of people "x-bugyo(奉行)" (e.g. nabe-bugyo, sushi-bugyo) as irony. bugyo means a person in a high position in Japan's feudal period.