I've never tried duck flank in combination with the chenille,but those look great. Flank feathers are easy to dye,been dying a lot of my own for about five years,using Cushings perfection dyes. I buy gallon size bags of mallard flank,trim the fluff,wash and throw it in a pot,heat ,add dye and BAM,dyed feathers.Actually,I put the feathers in after dye is dissolved completely.Otherwise da feathers may turn out speckled.