For excluding subscribers from any list you just need to deselect the list the subscribers are already in.
As shown in the following image, I wanted to send a campaign to my default list but wanted to exclude a few email addresses which are in List 5, so I deselected List 5 and selected the default list, before sending my campaign.
As shown in the following image, I wanted to send a campaign to my default list but wanted to exclude a few email addresses which are in List 5, so I deselected List 5 and selected the default list, before sending my campaign.