A few thoughts; lack of infrastructure for pedestrians and cyclists is what crowds us together and forces close passes, try to remember this and be patient and kind.

The individual being passed has the right of way, they have no obligation to make way. The individual passing is responsible for doing so in a safe manner, no passing on turns or where view is obscured, sometimes need to slow down and wait before passing. Always wait for opposing traffic to clear before passing, don’t dart out in front of opposing traffic making them slow or take evasive action.

A bell is the most effective and least startling method of alerting others to your presence. People seem to instinctively move right when hearing a bell. As mentioned by OP, calling out on your left sometimes makes people move left. (Not true on group rides with experienced riders, on your left is the correct method there)

Source, decades of cycle commuting and pleasure riding.

Edit: directionally challenged