Scrapping material sent back on an RMA PO

I don't know how to process a scrap receipt against an RMA PO.  Initially I thought it could be handled through a scrap receipt routing step but according to document 1345582.1 Receipt Routing FAQ, receipt routing cannot be used with RMA (question #10).  From the RMA document 625416.1, on the RMA defaults setup (P40052) there is a scrap BP and location that can defaulted in but I've scoured the rest of the document and can't find how that works.  Plus we don't know when the RMA is created if the item needs to be scrapped until we receive it back.  Can someone please assist to let me know how this works? Often times, when the items are returned against an RMA, we just need to scrap them.  Most of our RMA processes involve creating a sales order as a replacement part and we also create the PO