This is just a quick guide to give Oliver a good idea of the technique for split thread dubbing.
I haven't bothered to cut the marabou fibres down as it was just a quicky but you can do this to make tighter dubbing.
Once you have threaded your hook, tied in your ribbing and fixed the tail, split the thread by pushing your nail against it to spread the fibres and insert your dubbing needle, splitting them evenly
Hold open the two sides of the split and insert your dubbing material
Let the thread close and spin your bobbin in order to twist the fibres together
Wind on your dubbing rope, stroking the fibres back towards the hook as you work up the shank
Run your rib up the shank weaving it in between the dubbing fibres to avoid trapping them
Finish off your fly with whipping and varnish