Firstly, I would like to say that you should not speak loudly to be persuading. I notice that the quieter you speak, the more people listen to you.

Anyway, this phrase has some meanings. The first one is that words without actions is hollow talk only. Nobody likes a person who doesn't do anything but speaks a lot.

The second meaning is that actions (I mean the language of gestures) is the most simple way of communication, especially in case of international communication. What's more, it is the only method for deaf people.

I agree, very often different countries have the opposite meanings of the same gesture, so you should be very carefull. It's a good idea to figure out such details in advance. Also I would like to mention that business conversation cannot be based on non-verbal language. For example, any arrangement must be written using words.

However, I would like to repeat that in most cases the language of actions is the most simple and understandable one. It is very usefull for fast getting information about the current time or about the route to the nearest shop in unknown country.