I´ve used this plugin to import tens of custom posts in a WordPress multisite install.
The process is extremely simple and well explained on the author´s website. This is how I did it:
- Create an example post, similar to the ones you want to import
- Export this post using the plugin´s export feature
- Open it with Google Drive Spreadsheets, using the comma as delimiter
- Create a new row for each new post you want to import (detailed info about each item can be found on the author´s website)
- Export the spreadsheet as CSV file (again, using the comma as delimiter)
- Import this file using WP CSV into WordPress
All in all this plugin is a real time saver for batch creating posts.