The mermaids fishtails looked to shiny to me so I experimented by painting on scraps of fishtail fabric ( its a metallic knit stablized on freezer paper for these trials — on steam-a-seam 2 for the quilt) here’s a before of this shiny stuff; 
For these trials I assembled Shiva Paint Sticks, Jelly Roll pens, Fabric Mate Markers and Sharpie fine points. 
I tried a purple and green Fabric mate
and purple, green and blue jelly roll inks. This next picture shows the Sharpie Fine Point colors of green, purple dark blue and turqoise. 
And lastly the Shiva paintsticks:
The top color is from directly applying the stick to the fabric, the next was applied with a sponge brush the third was from blending directly onto the fabric and the bottom is from blending purple,green and blue on a scrap of parchment paper and then blending it with the sponge brush and applying it with the brush.
I think that last blend is great colorwise.
Conclusion: I wanted coverage that still allowed some shine through and also highlighted the scaley look of this fabric.
Fabricmate: some shine, good texture, colors are too neon for this application
Jelly Roll Pens: dull colorations, not much texture shows through, a bit of shine
Sharpie Fine Point: Deep colors but almost no shine or texture
Shiva Paint Sticks: Direct application yielded almost the same results as Sharpie, but when the sticks were blended on the parchment and then sponge brushed onto the fabric — great result: good color, texture and shine. We have a winner!
So now I tried it on a mockup of a mermaid tail: 
Looks pretty good, but I want it to vary from light at the belly region to darker at the fins, so I added som green FabricMate to the fin section and a bit more blended blue/green shiva stick to the mid section. Can you tell a difference? I don’t think the photo does it justice. 

















