Long ago someone used a florist's frog to process sinews. If you don't know what that is, google the image. Basically the thing is a puck with a whole bunch of sharp nails sticking up. Florists put it in the bottom of a vase and then when they poke flower stems down into the vase they stay where they are put.
I had no idea where to find one, so I took a piece of 1x2 hickory scrap, drilled a lot of holes, and then set skinny little finish nails into it. Kinda like carding wool, I carded my deer backsinews through it to break it up. Short and broken pieces stay behind in the tool, but I stashed those in a baggie and saved them for glue. This process has worked for me for decades and I think sinew makes a superior glue to hide glue!
Maybe that's my next project? Show how to make one from scratch and how it's used.