Thank you Russ, my fine art and design studies help for this. This is the only help they're giving in my daily life, and sadly not the most useful.

Just beautiful.
Vallejo Black Primer
Russian Green Acrylic airbrushed.
Mix of Tamiya brown paints as the rust base color, airbrushed
So, the Tamiya browns...did you just lightly and randomly brush these over the Russian Green? No HS in-between?
Marc,
Actually the first russian green layer was an happy accident. I first wanted it painted in regular green scheme, but changed my mind in the process and gone for a wreck. So, no HS in between and I've just painted the dark brown over the green, trying to cover everything but staying light in the thickness of the coat. Then when I started chipping later, some gentle rubbing with acrylic thinner made the first green layer appear. Everything's blend after with the filter, so it just gives a sense of depth in some place but it's not so much visible.
The process isn't very controlled and regular, because by brushing the Hairspray, I've often done successive layers of chipping on the same place. There's no definitive Rust + Color layers in the piece, but rather successive worked and reworked areas. Sometimes I've airbrushed rust again on top of the already chipped light green, but always trying to keep the previous coats viewable. So staying light and thinned at each steps.
Also, sorry to be a bit boring, but this is the kind of thing you can't say with pictures. But I think that processing by really small areas really helps for the general look. I mean, I can't have this result by doing the whole turret at the same time. It's just plenty of different zones, and when I had pin washes done at some places, I was still in the base rust color at others.
At the beginning it seems weird because of the patchwork look, but at the end, everything's blend with filters and dusting.
Going back to previous steps for enhancing some areas is really the key.
On the very rusted area at the bottom of the turret, e.g. I had all the pin washes and all the streaking done, but I thought it was looking to wet and grunge, so applied over this already weathered area a very thinned coat of tamiya brown acrylic, to desaturate and blend the whole.
Many AFV modelers are being used by the HS technique instead of using it.
Once chipped with water, this is by no mean the end of the chipping process and many are just going to the next steps because that's how things are written in the magazines. But often then, it gives too harsh and sharp chipping even though the reality is much more layered and delicate.
If you're staying light and thinned, you can literally add hundreds of new layers on top before having a thick feeling and hide details.
Every time I'm spraying over already chipped area, just to blend, and create finer and finer layered chips.
It's just a bit like 3D impressionism. It's the global visual look against the definitive and delimited "steps to do".
Sorry if I sound a bit know it all on this, it is not meant to lecture anybody, just trying to say what we never read in magazine's SBS because I'm sure many are working that way.