This sounds more like an Isonychia than the Brown Drake. Brown Drakes are actually a cream (or golden brown) color with brown highlights in the wings of the dun's grey wings. And the Brown Drake spinners have this same cream to golden brown coloration.
Isonychia spinner are a mahogany (reddish-brown) brown and would be #8 or #10 in hook size. Just tie a spent wing spinner with light dun tails, a reddish-brown dubbed body, and spent wings of either very light grey poly yarn or a light dun and grizzly hackle wound and then clipped top and bottom (you can simply just clip the hackle on the bottom and then have the top of the hackle to help you see the fly). Tie it on a #10 or #12 2x long, fine wire hook.