Can you create a picking in odoo manually so putting in the requested amount. 
Then confirm the picking

So 2 persons can handle the outgoing stock:
person 1 is responsible for creating the pickings with the required products and person 2 is just responsible for sending the products to the customer. 

This seems to me very likely like the flow from a sale order without that initial sales order. 
I haven't found it yet how I can set it up in odoo.