Buying Guru allows you to automate the purchasing of products that have dropped below your minimum stock on hand levels.  It will populate purchase orders for exactly what you need to maintain optimum stock levels.

A pre-requisite is to ensure you have setup or imported your min, max and par levels and have set a default supplier on your products.

To review and purchase products who's stock on hand is below minimums, open Buying Guru (Purchases -> Buying Guru)

Select the Warehouse and Supplier from the drop-downs and click Run Report.

Review the results and click Order these materials to raise a draft stock purchase order.  The shortfall quantities will be the default line item quantities on the purchase order.  If you need to change the quantities, you can do by editing the purchase order once raised. The Order greater of shortfall vs min order qty? option lets you toggle between purchasing the product's minimum order quantity (if set) if it is more than the shortfall quantity to ensure you aren't purchase quantities the supplier won't fulfil.

Approve or edit and send the purchase order as per the normal purchasing workflow.

Even if the purchase order has not been received, WorkGuru tracks that it has been raised and will remove the ordered products from Buying Guru to prevent duplicate purchases or over-ordering.  Cancelling or deleting the order raised by Buying Guru will return those order lines to the report.