A man named Russ Fairfield wrote a big "dissertation" about finishes on a forum called Wood Central. Here is the link to the article.
http://www.woodcentral.com/russ/russ3.shtml Here are the links to the oil finishes.
Tung Oil
http://www.woodcentral.com/russ/finish6.shtmlWipe-On Varnishes and Oils
http://www.woodcentral.com/russ/finish7.shtmlThe MSDS sheet for the Tried and True said it contained 80% modified BLO and 20% Sylvetac Resin.
Modified BLO is usually diluted BLO using mineral spirits or turpentine. The Syletac is the trade name for turpentine based varnish.
I have chased the "magic" woodworkers finishes for over 50 years. If a finish has been sold, most like I have bought it, I have made a few hundred "secret" concoctions that are only known to God. Today for an oil finish, I mix BLO, turpentine or mineral spirits and a good brand of spar varnish. I only mix up a small amount at a time, it will cure in the can if not used soon enough. I buy the BLO and turpentine at a big box store, a 32oz cost about $8, 32oz of turpentine costs $7 and a 16oz of Helmans Spar varnish is $16.
To mix it, I look at the MSDS sheet of the one I want to copy, in this case 80 20. The 80%, I would add in what I feel is a good amount of turpentine or mineral spirits. I usually start with about 2 to 1, 2 parts of BLO and 1 part of mineral spirits. Then the 20% varnish.
I had a note book with all of these combinations, but because of health issues, and my shop being closed it was lost in history, If you go with trying home brewed finishes, TAKE NOTES, your memory is not as good as you think. This way if you like a ratio, you can easily duplicate it 2 years from now.
My method of finishes is the Frank Whiton Classic Gunstock Finish. No it is not classic as in the 1700's, but his name for it and used on modern day weapons.
https://www.firearmsforum.com/firearms/article/3037 If you read his method, you will see that he dilutes it for the first coats, I mix mixed small bottles for each ration. Keep the bottles out of the sunlight and in a cool place.
Cost of the above, $31, and I have enough to make 64oz of finish. Unmixed, the only ingredient that will go bad is the varnish, so I buy the smallest cans. I have used this finish on just about everything, from furniture to cabinets, to gunstocks.