I've never found enough placer gold to ship........But shipping scrap jewelry. It's been a few years...The one refiner paid the shipping. Just weighed it,Packaged it up good, and took it to fedex with a number to give them. Then once I had my receipt I was no longer responsible. If it came up missing? Supposedly they (refiner)would have still cut us a check as long as we had our receipt or a confirmation. We called it in first to lock prices at times. And that is when they give you a shipping number or id number to give fedex.
Never had any come up missing or lost. And I shipped 2 to 3 times a week at that time. Some nervous times! Kind of scary just shipping it off!
Your best to call the refiner and ask! They will tell you who the best is to use and what to do. I WOULDN'T send any amount without first talking to the refiner you want to use. If your going to ship A lot, there will be paper work to fill out. I forget where that line or amount is. Patriot Act stuff.
That may only apply if your getting a check or transfer. If it's on a service or trade? It may not apply.
The refiner your going to use is probably the best source for answering any questions.
Added...
Years ago when silver went high....My Mom and Step Dad sent me over 7 thousand in silver in coin to sell for them through the mail. Just a USPS, Priority box. I WOULD NOT ADVISE THAT!!!!!!!!!!

Then, it was left on my front porch. When I got home, felt this heavy box on the porch, Opened it, saw the note"please sell for us! Love Mom", and I about passed out!! Thinking of how fast that could have came up missing!!! Especially, where I lived at the time.