Which descendant of Cain was a forger of bronze and iron tools?

Answer: Tubal-cain

Zillah bore Tubal-cain, a forger of every implement of bronze and iron (KJV: "an instructer of every artificer in brass and iron").

“And Zillah gave birth to Tubal-cain, a forger of every implement of bronze and iron. And the sister of Tubal-cain was Naamah.”— Genesis 4:22 (BSB)