Hi Ian,
Thanks for raising this on the community! Just to clarify, is your question how can you sell your own beer to another brewery at 0 cost as a swap, or how to sell a Guest beer that you have received from another brewery? Breww will allow you to facilitate either by mapping the Sellar product to either your own beer or a guest beer product in Breww, depending on which of these you are trying to achieve, but the cost will always be given to Breww from Sellar, so you will need to ensure this is set up correctly based on your intent for the customer purchasing.
If you haven’t set up any Guestbeer products in Breww before, you may want to check out our 📘 Introduction to products guide, which has more information.
Let us know if you have any questions at all.