Bill Eadie shares with us a pattern that has been catching him some good grayling
The Grayling Slayer, as it is called, has been devised and tested over the last few years. The idea was to have a small fly with a heavy bead to get it down in the water column quickly. The mylar ribbing adds as an extra trigger point along with the orange collar.
I have given the fly to friends who have reported similar success. I hope you tie some and try them out too.

Here's how to tie the Grayling Slayer
You'll need:
Hook: Dohiku jig claw 14,16,18
Bead: 4mm, 3.5mm, 3mm copper
Thread: White Semperfli Nano Silk
Body: Very coarse grey and fox squirrel blend
Rib: Fine Mylar size 16
Collar: Hends Spectra dubbing no 294

Run on thread and tie in mylar

Touch dubbing with sticky wax but don't roll it and keep very sparse and spikey

Run the rib up the hook with 3 turns maximum

Dub on a slim collar, whip finish and really pull in tight to secure collar on hook shank, it is vital to do this.