If it is famous, you will require less persuasive copy than if it is unheard of. Because one maxim is that long copy always outpulls short, bad writers often write far too much. All you have to do is give every sensible reason why your prospects would want to act and overcome every reasonable objection to acting. Never use a single word more than required. A salesman would try to demonstrate the product.
Good communications do the same thing, either in words or in pictures or both.
Sometimes a direct mail pack can literally demonstrate the product. Nothing convinces more than an involving demonstration. If your name is well known, feature it strongly As I have pointed out to you, this could double your response. But make sure it is well known. Most people can only remember about three brands in a product category, until they are prompted.