The clear butyrate are the fill coats. Filling in the weave of the fabric. They come before the colored butyrate.
Pigmented dope is heavier than non pigmented dope. So you fill the weave with clear and use as little colored as possible.
I'm spraying the last few fill coats this time because of what I learned doing the Krier. I brushed all of the fill coats for it and only sprayed the color. The end result, while good, wasn't good enough for me. It still had some faint visible brush marks even after sanding and 2 coats of color. You can even kind of see them through the urethane clear.
I don't want brush marks in the Kanary and certainly not on my next project so I'm spraying the fill coats from here out.
This method more closely follows the Ceconite STC (full scale dope and fabric process) as it actually only calls for the first coat of Nitrate to be brushed. Followed by a sprayed coat of nitrate and then 6 coats of clear butyrate, 4-6 coats of silver and 2 coats of color (more color coats if you want a shine because you have to polish it, as its not legal to use clear coat to make it shine, or you have to use urethane paint).
This being a model I'm shinking that to 4-5 coats of butyrate, no silver (UV protection) and as little color as possible to keep it light.