I don’t know of any secret technique, just a ton of repetition. For example I might advise a student to take all the words from COWS RAID (verbs that attract the subjunctive: command, order, wish, require, ask, insist, and demand) and IN ICE (adjectives that attract the subjunctive: important, necessary, imperative, crucial, and essential) and write a dozen sentences for each. It’s not a thrilling task to be sure, but by the end it should be more intuitive.