For 99% of my flies, shiny side face forward. Where I don't is when tying a Neversink Skater where 1 hackle has dull side facing forward and 1 is shiny face forward. Then push together. Another is sometimes when I tie a 'variant' I'll use a similar way of wrapping the hackles but without pushing the two together. On the former, that's how it was tied by Hewitt and Darbees. I have absolutely no idea on the latter if it makes any difference.