Hi Vincent
Could agitators help in the AK bottles?
You can get steel or glass balls but I actually got stainless steel hex nuts after researching the problem.
Why?
More surfaces to agitate, a sphere is too regular, a hex nut has lots of uneven surfaces to break up the thicker lumps of pigment.
Does AK have a glaze medium, like Vallejo?
it is great to thin out thick paint and use as a glaze medium too, it is made of the same formula as the paint, so it gives a better suspension of pigment when thinning,it is much better than just plain water.
Practice is the last part of the formula too, but your work is already getting there and certainly well on the way, I took a year to get this far, and am still learning.
Keep at it
Regards
Steve H