When I ordered my lowers, they had a section to fill out for your dealer's info. I just called around about doing a transfer and picked one from my short list. Used his info and then emailed him to let him know the order was placed and left him their fax number. Went smoothly.
Did you pay one FFL fee for all the lowers or was it one per lower?
Never bought anything through mail where I had to get the FFL, always been in person.