We used to implement Blogger custom FTP for clients, but now are no longer recommending its use. Blogger custom FTP is where your blogger account is set up to allow your blog posts to be archived back on your own domain server using FTP for search engine benefits.
The problem with Blogger custom FTP is that it is easily crashed, sometimes can take hours for the FTP part to send the posts to your server, and if you have a custom template can be fraught with problems.
If you want the search engine benefits that a blog affords, I strongly recommend that you use WordPress back on your own server. Upload and posting time is very snappy and you won’t end up at the mercy of Blogger when they do updates. We migrated several customers several months ago when Blogger had a reported bug for custom FTP clients as it took two days to publish blogs.
Another issue with Blogger custom FTP is label bloat. If you end of with many labels on your blog, get ready to spend hours deleting them as your publishing time will move to hours from seconds. The best option if you simply cannot use WordPress is to use Blogspot with a custom domain setting. We have found out that you really do not take a hit with the search engines when you are not using custom FTP blogging.