So after doing a quick image search I see that the scales are shorter and wider.

If you wanted to make them look textured and shimmery you could possibly use a finer point brush to dab more intense and whiter color on top of a darker base color. Blue should be pretty easy to pull it off with

Have you looked up any of the other threads on painting a tail? There are a lot of good tips you'll wanna use, such as stuffing your tail with something so that the material is stretched out and you won't end up with crackly paint when you put it on.
One thing you could maybe do if it works for you- I've not done it myself so I can't particularly vouch for it, though I've been eyeing it- is to do a screen printing/stencil approach. You'd take an embroidery hoop and put something like organza or some sort of mesh fabric on it. Trace or draw your scale design on it, trying to keep each scale the same so that it matches up, then put white glue anywhere you would not want paint to go through, such as the outline.
When the glue is dry, you'd use it as a stencil, applying your paint on top so it goes through.
The main advantage to using this technique would be that you'd get consistency. It might also be messier though, depending how the paint squished through your stencil. If it were me though, I'd do a test swatch first, using the stencil to make a base layer of color and putting more layers of color on top to define the scales.

Anyway it's just one way to do it.

There's also this method, using a piece of plastic to do one scale at a time, and maybe look at these swatches. They're lovely