Depending on the shipping methods you're using you may be able to complete all tasks in your Order Manager (vetting orders, printing packing slips, printing shipping labels) and then pack in GroovePacker without needing to return to your Order Manager.
In some cases, many or all, of the shipping labels can be generated when the packing slips are generated. For example, 80% of your orders may ship using a flat rate method. These could all have their labels printed before packing. Once the order is packed you would only need to attach the shipping label. This eliminates the need to return to the order manager to create the label after packing.
The other 20% could be done in a separate batch. For these you would return to the order manager after packing to weigh the order and create the label. Some companies use a rule in their order manager to sort the orders based on their shipping destination or items to automatically separate the orders into the two groups.