How do you get a slime knight in Dragon Quest Monsters joker?

I haven't found an extremly effective way but if you get powerful monsters with good weapons for the encounter you can psyche them up to 50 tension or 100 and scout him it will increase your chances but not by much sry all I know :( Then why answer? Metal slimes are ranked D and metal king slimes are rank S. You are a stupid guy! Call my number 1714-876-545-6