Hold your horses

. I only use artificial sinew for home testing , or general shooting in my wild backyard . Never for hunting . I use my rawhide/sinew/dogbane strings for that ! Besides , artificial sinew requires knowledge on two ply cordage .
Now back to the varnish/bacon grease , blah blah blah deal ! The closest your gunna get to a natural varnish replica is beeswax/fat combo or resin/fat combo . I don't think our ancestors would dig up some magical plant and find the root to be a bottle of varnish .

And now someone could argue that the use of one steel knife , sandstone , anf smaller flint scrapers still isn't primitive , but one could easily drive a 7 inch flake from a chunk of flint and substitute that for that steel knife / scraper . Along with a 14 pound rough sandstone for a rasp .
Use what you have . Now unto urgent matters ----------> im liking the tiller bud

!