You’ll pay back your initial time investment within a month or two, and you’ll end up with a dramatic improvement to efficiency and long-term retention, as well as teaching a useful tool/skill that can be put to good effect if the kid ever needs to memorize trivia for med school or bar quizzes.
Trying to cram-learn a new list of miscellaneous things every week is a fool’s game. The key to human memory is connections, context, and repeated exposure, not brute-force effort.
Personally I always just read science fiction books hidden in my lap during spelling time in school, and my teachers gave up on trying to get me to study lists of words I already knew how to spell. My older brother’s strategy was to just do poorly on spelling tests because he thought it was a waste of time: never seemed to hurt him, and decades later he can spell as well as anyone. YMMV.