I've refined "a lot" myself when I was having trouble with a refiner's accountability. They were shorting me. So to prove to myself that my numbers were correct, I refined my scrap gold.
My yields were spot on. The refiner WAS shorting me.
That said, once I found a reliable refiner, I stopped the refining. I gave away 3 gallons of nitric acid to a jeweler who wanted to keep refining. Good riddance.
Here's a 2 oz or so bar.
Frankly, refining is too much hassle. The 2% or so that a refiner charges you pays for a lot of headaches.
Oh, I use Safina Materials in Conroe, TX. They're chemists and chem engineers, like me, and can talk chemistry if we ever have a problem. We haven't had problems, btw.