"flattening" gloss varnish

white cedar

Curious about Wooden Canoes
Hi: I'm using Captains 1015 gloss varnish on a new boat. The first two coats of thinned varnish are on and I'm planning for the last two. I'd like to end up with a flat or semi-gloss finish. I understand that I could add a "flattening" agent to the Captains. Jamestown has a flattening agent manufactured by Interlux but I could not find a product manufactured by Petit. My question is, are "flattening" agents company specific? THANKS!
There is Captains Satin finish. I have some of that and it was actually a bit too flat for what I wanted. I think if you search under satin you will see some pics of the beautiful canoes done with that.