I’m not sure you’re answering the question posted.  The response indicates how to generate an invoice to the client based on the vendor's hours input, but I think the questions was "how do I create a bill", that is a charge from the vendor.  

or maybe I have it wrong.    Here’s what I’m contemplating.   For ease of tracking I wanted to have a  supplier input their hours into QuickBooks for tracking, however, how do I pay this vendor?  Or if  a vendor then invoices me and I put it against the project, I’m now double counting that vendor's hours.