You can easily block posts from specific users. Just enter the username into the “Disallow posts with these words” field, located within the “Moderate and Filter” panel of the Juicer dashboard. Enter the username lower-case, as shown here: 

If you are entering multiple users, be sure to separate the terms with commas: 

To complete the setup, if posts from the unwanted users are currently appearing in your live feed, click “Save your filters” and then click “Yes, apply to existing posts”. This will move the unwanted posts over to your “Moderated Posts” section. 

If no posts from those users are currently in your live feed, click “Save your filters” and then click “No, only future posts”. 

Remember, you can also turn on the “Send all posts to moderation” feature, if you wish to manually review all posts before they appear in your feed.