If you're looking for something on how to paint the Tyranid carapace, I did a brief run down of it on one of my threads over at the tyranid hive, though it's not really what I call feathering so much as streaking. It was in response to a question from someone asking how to get a similar effect using a purple carapace, so if some of it doesn't make sense, that would be why. But anyway....
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That purple Tyrant looks good. If you want an effect similar to mine, you just need to paint longer streaks and use a middle colour between the darker purple and the pink.
If you look at a close up of my Hive Tyrant (sorry for the poor image quality, this is taken from an iPhone 3GS
)...
You can see where I painted the enchanted blue (paint liche purple for a purple carapace)...
And where I painted the Ice Blue (paint light purple/pink for a purple carapace)
This Tyrant was actually a 2nd hand model that I repainted, so I didn't put a hell of a lot of effort into it, if you look at my Trygon (which I spent agggges painting) I went to a bit more trouble to hide the transitions and make the streaks slightly neater, though maybe you don't want to hide the transitions if you want a rougher, grainier, more natural and more textured look. If you look closely at the Tyrant you can see the wiggles and brush marks in the streaks, my Trygon is much neater... but from more than a few inches away you can barely tell the difference.
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Haha, I start at the tip [of the streak], usually just 1 brush stroke per streak, but sometimes you have to go over it depending on the colour (if you're using blood red it doesn't have very good coverage so you have to go over it multiple times).
So the brush is held with the tip of the brush at the tip of the streak and I press more of the "body" of the brush head into the model as I move downward to create the tapering.
Use a good brush that holds it shape well and is reasonably long and thin, rather than brushes that bulge in the center or are stubby and tapered (that's why I use a number 1 brush with most of the bristled removed rather than an actual fine detail brush).
Another tip is when you pick up the paint from your palette, roll the brush through the paint on to your palette and it'll create a nice tip ready to do the streaks.
A couple of models I really struggled painting nice looking streaks and then about half way through realised it was because I swapped to a different brush that was making life harder.
But it's really not all that difficult once you get used to it... but it is time consuming! Hence why I'm looking for a different scheme for my Termagaunts.
I can't really comment on your colour selection because I've never used any of those paints to know how they'd come out
Looking at the new paint range, hmmm...
Naggaroth Night base coat -> Xereus Purple streaks -> Genestealer Purple streaks.
But that's just going off the images on the website, I haven't seen the colours in the flesh to know if that's a good progression. Another option for something slightly brighter might be
Naggaroth Night base coat -> genestealer purple streaks -> Emporer's Children streaks.
But yeah, I'd go to a
GW store and ask if you can use the store paints to try it out before you actually buy anything. Based on the colours on the website, I'd be tempted to mix a bit of black into the naggaroth night, but in real life it might be dark enough, I don't really know.
