I have a found an easy way to replicate the blood pacts ritual scarring that every member goes through on initiation into the Pact.
For Cadians you only have the flesh of the hands but Catachan gives you alot more skin to scar.
What I've done is take a small paperclip,pin and heat it up the quickly and lightly poke a few shallow marks into the hand just enough to mark up the hand.
You can also heat up your hobby blade and lightly press against the arm and hand for realistic scars and gouges.
Then paint up as usual I have used dwarf flesh here with scab red wounds.