Hi Braedon,
It is possible to import customers to either create new customers, or update existing customers. In your case, all you would want to do is get a list of all the customers that belong to a particular control group, and import the single change for those customers to set them to the desired terms. That list of customers could be created from any of Export Customers, ExcelDirect from a filtered Customer list, or exporting from a SmartFinder search of customers.
Here is a link to a
short video of about 4 minutes on how to configure importing to update existing records, such as customers. The video is for Payables vendors, but the idea is the same for Receivables customers.