In a bullying situation involving two school-age children, which safety management technique would likely work best?

You need to learn how to avoid them and don't let them get to you, but if they hit you then that's another story.

Speak up. You should tell an adult you trust. Have a talk about it with them, let them know the situation and ask for advice. Ignore the bully(ies), walk away. BUT you should stand up for yourself. If you stay quiet and let individual bully you they're going to think it's okay and continue to do so. Watch what you say, though, it could cause more problems.