A blogger subdomain on a wordpress.com domain

As it turns out, it is not difficult to edit DNS records in a domain registered via Wordpress.com to create a subdomain in a domain you're already paying for. Since I rarely mess with it, I always had a reluctance in cutomizing DNS records. In fact, I don't have a good understanding of DNS stuff.
This blog's only URL used to be flaguser.blogspot.com. For some reasons in the past, I chose wordpress.com to write my other blog (which has a more unified theme) and ended up registering the flaguser.com domain via wordpress's service for ~35 usd/year (I felt a bit sad finding out that it's just ~10 usd/year in blogger. That's a ~2500 usd difference in a hundred years!). Well, anyway here's how:

1.  Edit your wordpress.com DNS records (Admin > Store > Domains > Edit DNS)
2. Add the line:

CNAME blog ghs.google.com.

Note: I wanted "blog" to be the subdomain. Change it accordingly.

3.Validate, then save.
4. Add your custom domain in Blogger (Settings > Publishing > Blog Address > Add Custom Domain > Switch to Advanced Settings)
5. Write something like:

blog.flaguser.com

TIP: From what I've read, a similar procedure also applies for Google sites.

References

1. Custom DNS (wordpress.com support)
2. How do I use a custom domain name for my blog? (Google support)
3. Mapping your site to your own URL (Google support)