Do what i did. Do the mission for rusty first and then do the missions for debris walkers. You'll get the rewards for both options if you kill him for rusty, and then tell lang that you completed it
No, I got a reward from both of them, Lang gave me 200 gunpowder but Rusty only gave me 50. I was trying to get 200 from both of them when not killing Dillon because if you kill him for Rusty and get the 200 from him, providing him with Dillon's hair was good enough proof of killing him.
That's why I was asking Icy if we could still cut off Dillon's hair as well when not killing him, so that we could get 200 gunpowder from Lang AND Rusty going this route but Icy doesn't want us to be able to get 200 from both of them.
So Icy is going to change it in the game so that we will cut off a finger as proof of his death, like we do with the bounties. The funny thing is, we could tell Dillon we'll let him live but only if he allows us to cut off one of his fingers as we need it for proof of his death for Rusty and he would probably agree to it.