If using the conversation window to send SMS to a contact you are able to quickly add a template to the message in the same way as you would when creating a group message.
Simply select the template icon as outlined above and choose which of your templates you wish to use from the available ones in the menu.
Selecting the required template will populate the message window as below. Notice that as the template may have been set up with data tags such as the 'contacts-fullname' example below the system will automatically populate the message with the contacts data. You can edit if desired before sending.