How do you get the correct items in for each customer?
BSimple has an automated system in place which will analyse past invoices (imported via Xero) and build a list of items with the relevant pricing based on this history.
2ND to this, BSimple strongly recommends for the first few weeks, placing all orders on behalf of the customers. This will give you intimate experience using the system, and the insight to check and fix any problems you see on customers order pages immediately. It is important that you are familiar with the system, because your customers will expect you to be a pro and be able to provide telephone support.