When using verbal commands, please do not use the instructiones left or right. Due to nature of the activity, driver and spotter are face to face, left for the spotter means right to the driver and viceversa, that is why you come out with wording like this: "right, your other right…"
Instead, use driver or passanger commands (piloto o copiloto in Spanish), in that way no matters what spotter or people say, all understand the same.
Engine noice and others people instructions leads driver to ignore outside verbal instructions, focus on hand signals only.
Better than verbal commands are hand signals. Keep eye contact with driver. Choose a place, different than main line to spot driver, could be a rock, and provide as much information as you can to the driver. If a tire will go over a rock, let the driver know in advance. If a tire go down due to a crack or any other obstacle, let the driver know.
Trust between driver and spotter is not expontaneus, you need to build it. People will trust the spotter when they realize the work that he is doing and watching other people going sucesfully over the obstacles.