Highlights for the black armor? First a semi-sloppy highlight of roughly 50:50 Chaos black and codex grey (not exact measurements, just had to eyeball it til i got the shade i wanted). Second a very fine highlight of codex grey. Keep the brush fairly wet and take your time or else it ruins the blending- if you go without watering it down or lay it on too thick at once it's just as bright as Fortress grey. Simple and straightforward but still a bit time consuming.
The one big advantage is that the 50:50 mix doesnt show up particularly well in average room lighting, so it does it's job as a blender for the highlight but you dont have to be very precise at all. The big disadvantage is that it shows up even worse when the paint is still wet, so you'll have a hard time seeing just what you're doing. If it gets too out of hand, all you have to do is clean it up by pushing it towards the borders with more basic black afterward.
As for the notes about personalization on shoulder heraldry, yeah i was counting on that loophole
. The shoulders take the most time of any part of the model, and i even paint them separately before attaching just to make sure i can give them proper attention. Since I cant make a perfectly identical cross over and over (or even twice in a row) I decided to have a little fun with it and try to make each one unique in its own right. Plus mixing in a standard BT plastic shoulder on each model keeps it feeling uniform at the same time.
Sometime down to road I might even go back and start adding white scripture on the armor like most folks tend to do, but for the moment I'd like to actually get a fieldable army painted for once