Bulk processing cust/vendor payments

[yary]

I'm converting into GnuCash my businesses books from an on-line system that
went down mid-year. Successes so far- loading customers, vendors, invoices
and bills all via "File->Import" and csv files.

I am also able to convert all the records I need into QIF and import them
into GnuCash. However,the QIF import makrs none of the bills or invoices as
"paid," even though the A/R and A/P, bank accounts are properly
credited/debited.

1. Is there any "bulk process payment" for bills/invoices that reads a
file, of any format? If there is, then I'll use that, and remove the
matching transactions from the QIF

2. If #1 isn't possible, then maybe I should keep they payments in the QIF
file and mark invoices as paid using SQL. Is setting "Lots.is_closed=1"
completely sufficient for marking an invoice as "paid"- or do I also need
to tie the payment transaction guid to another table?

I've browsed the ERD at
http://wiki.gnucash.org/wiki/images/8/86/Gnucash_erd.png , and also paid a
couple invoices through the normal interface to see how the tables change,
but still not sure I understand all that changes when processing payments.

My day job involves SQL and text-file processing, so I'm comfortable with
creating files, updating tables as needed for this task.

-y