The method is actually based on sending SMS using some online websites that will allow you to send SMS without entering any personal details. So just have a look on the websites to send free Anonymous SMS.
This is the one of the best site that supports 160 character message to send to any number online and you will not need to register any personal details and can send free SMS to any of number. Must try this.
This is one of the best anonymous SMS sending portal that allow you to send any message all over the world that absolutely free.