Mixing hackle fibers to form a tail on a fly like an Adams isn’t difficult, but this little trick from Charlie Craven really makes it easy.
Strip 8 or so grizzly hackle fibers free from the stem while keeping their tips aligned. Snip the curlies off to keep them from snagging your thread and to reduce bulk.
Lay the butt ends of the fibers against the near side of the hook as you give your bobbin a gentle counterclockwise spin. Secure the fibers to the shank with just one or two wraps of tying thread. This position is only temporary.
Repeat the same prep procedure as before, this time with brown hackle fibers. Holding the fibers in your right hand, align the hackle tips precisely with those of the grizzly hackle. Get hold of all the fibers with your left hand and unwind your tying thread 1 or 2 turns to free the grizzly from the hook. Measure to form a tail about a hook shank in length.
Transfer this measurement rearward to the start of the hook bend and using a pinch wrap, secure the fibers as normal to the hook shank. The passing and tying-in process generally mixes the fibers pretty well.