We are on World but I believe the business process is very much the same. We have been doing EDI for 20 years, and dropship now for over 10 years with several of the largest US retailers. That being said, we don't send the ASN until the product is actually shipped. We do it this way in order to avoid potential chargebacks.
But check out Opal - they might be exactly what you're looking for: www.meetopal.com