Selective expandable post in new Blogger

At first, I try to implement the code from Blogger Help. I succeeded to establish expandable post in this blog but Read More links appear in every post, and that is annoying. I try to play around with b:if condition tags but failed eventually. I guess I do not have enough knowledge and experience with Blogger conditional tags.

My idea of using b:if tags is to create an equation. If span class id fullpost only contains "Type rest of the post here", Read More links will be hidden. If the text in the span class not equal to the default text, Read More links will appear. If I know a bit of javascript, this might help, I think...

As a final measure, I used Ramani's hack from hackosphere. It works but same problem appear again. Read More links appear in every post. Thus, I modified the code a bit. Instead of putting

span id="fullpost">Type rest of the post here</span

in the post template, I put the code manually in post editor. It works. Now, Read More links will only appear in any posts that I choose :).

UPDATE: At first it works, but later it fails miserably :-L Now, it works. The reason it failed previously is caused by putting the javascript in the body section instead of head section :)