Brand values add credibility to your products and helps to attract more sales. But, while listing products on your shop, it is not always that you add brand as attribute. If you have managed the Brand information using tags on your shop, you can still send those tags as Brand attribute to the merchants. Simply using this command to assign product tag as brand will help.
mapAttribute tag as brand
Now, hit update to let ExportFeed supplant brand attribute with the product tag that you have managed.