And I'd like to show how I implemented to this blog.
1. Save a backup copy of your template before you start. Just copy and paste all your code to a text file on your hard drive, so you can replace it in case anything goes wrong.
2. Paste the following code in your header. I add it just before </head> tag.
<style>
<b:if cond='data:blog.pageType == "item"'>
span.fullpost {display:inline;}
<b:else/>
span.fullpost {display:none;}
</b:if>
</style>
3. Adding "Read More" Links
Go to Layout and click EditHTML. Add a tick to Expand Widget Templates. Then add the following code to your template, after the <data:post.body/> tag:
<b:if cond='data:blog.pageType != "item"'><br />
<a expr:href='data:post.url'>Read more!</a>
</b:if>
You can replace the "Read more!" text with Continue Reading or Read the rest of this entry », etc.
4. Post Modifications
Go to Posting and create a new article. And wrap your article which you want to hide with the following code.
<span class="fullpost">
Your main article here
</span>
That's it folks. Thank you for reading.