Does anyone have recommendations for hiring a virtual book keeper?

I run a manufacturing company and I am looking for a virtual book keeper that can help us track bills on an accrual basis, and facilitate payments and track profitability. Ideally, this person will be able to send invoices, match inventory from our ERP with our accounting system, and generally clean up our accounting system (which is currently done on Quickbooks).

Does anyone have experience with this? Generally, what is required from a cost perspective and what is the lift associated with training a Virtual Assistant on the specifics of your business? Any recommendations for services are appreciated.