Maybe some other folks can chime in, because I'm curious as to how other shops and site sponsors do this as well.
I've done two transfers in the Vegas area, two different methods:
Shop 1): Buyer meets seller and negotiates sale. Buyer pays seller. Buyer performs BGC paperwork. Both buyer and seller offer NVID, shop photocopies both. Shop holds weapon until BGC returns. Buyer picks up weapon. If the BGC doesn't come back in buyers favor, seller has to perform a BGC to retrieve weapon back.
Shop 2): Buyer meets seller at shop and negotiate sale. Buyer performs BGC paperwork. Both buyer and seller offer NVID, shop photocopies both. Shop copies weapon serial # and all terms of the sale, charges transfer fee, and returns weapon to seller. When BGC comes through, shop contacts buyer. Buyer and seller arrange to meet at shop again, transfer money and weapon. This method seems like a bypass of the Sisolak law.