- Invite user "graddit@gmail.com" to be an author of your blog (Blogger Settings → Basic → Permissions → Blog Authors → + Add authors);
- What for confirmation (leave a comment to this post to speed up the process);
- Make graddit@gmail.com an admin of your blog. This is required to update posts by your request. Later adding graddit@gmail.com will not be necessary, but this is how it works right now. You can also revoke admin permissions once you are done with snippets and give it back only when you need it;
- Subscribe. You can also leave your blog address in a comment to this post and I will give you 2 weeks of trial;
- Login to admin, create an account if you don't have it yet (click "Generate secret key" for insctructions);
- Go to Statistics tab, locate a post you would like to update (you may want to save your post first, just to be safe) and click star icon:
It will try to retrieve Blog ID and Rating ID and will show a confirmation window:Click Ok. If system shows status "Ok", your post was successfully updated with ratings snippet. It can pass few days or even weeks before stars appear on SERP, but you can check if snippet is formed properly by checking URL of your post in this Google tool.
Disclaimer, recommendations and known issues
This will access your blog upon your request and will update post adding snippet to the end of it. It potentially can damage post content, for example, it will remove any newlines (not the <br/> tags that will remain, but \n - newlines that will be deleted), because this is how the posts content is presented by Blogger API and I could not find a workaround for it, so this method is not good if you have text in <pre> tags and want to keep newlines. In other cases removing newlines will not affect post layout. I strongly recommend to test it first on a test blog or test post. Also, do not update each and every post, Google might not like it, instead pick content that deserves to have snippet in SERP. Google does not guarantee snippets on SERP even if there is no errors in snippet code, that is stated in their documentation.
Try it and let me know here if you have any issues.