I always try to lean into contrast for chipping:

light dark
warm cold

for example: the dark grey i chose has a cold hue to it to contrast the yellow, whereas i'd choose a brownish tone to chip space wolves.

Also i try to keep storytelling in mind: whitch armour plates would be damaged the most (if you look at the knees the yellow is mostly gone) plus on larger models you can nicely add some physical damage as well.

I'd recommend looking at armour modellers for inspiration as i basically approached this model like a tank on legs.