Here's where I was able to find many of the products needed.
https://woodfinishingenterprises.com/ The venice turpentine is a plasticizer. It makes the finish more flexible and less brittle.
I suggest making the slacum outside or in an open garage. It has a pretty strong odor when you are heating it. I heated it for about 45 minutes to a very slow boiler. I still get a very small amount of precipitate in the bottom of the jar but just shake it up before making down my small mixes.
I spoke to Dennis Potter yesterday and he was very helpful. He has much more experience than I do. He gave me a better understanding of rubbing out the finish using a small piece of cloth covering a small eraser and rubbing with rotten stone and slacum. I tried it today with very good results.