Thanks! I feel like they could be cleaner but at a certain point you just have to call it done.

The black lining is Drakenhof Nightshade shade paint brushed around the edges of the blue armor right against the gold trim. After the shade I paint over it again with Thousand Sons Blue to make sure there’s only a tiny bit of shading next to the trim instead of a big stain over the whole blue panel.

I mostly followed this guide: https://www.goonhammer.com/how-to-paint-thousand-sons-the-games-workshop-method/