How can I automate USPS package selection for order fulfillment?

[TKK1]

I have tried numerous extension apps and cannot find something that works for my variety of needs.  All I really need is to have shipping rules available so that purchases are not all put into the default shipping box.  My needs are simple, as I can select boxes by weight alone.  The employee that does order processing should not have to manually select the proper USPS package for every order.  There really has to be an easier way that I cannot find.  I have it so the customer is playing the appropriate price for shipping, as those rules are available, but I need the backend support to then select the correct box for the employee tasked with order fulfillment.  Am I just missing it somewhere?????