I took off four months this year to do nothing but squash leeches 40 levels of accumulated leeches.
A few tips:
#1 For kanji leeches, writing them out helps tremendously I find. It makes me focus on the composition of the kanji and the composed radicals, which is usually enough. I make a note of leeches after a review and write them when ever I have time.
#2 For leech vocabulary, I’m here to learn kanji, so with pairs of leech vocabulary, I first ask how much I want to learn the leeches. There are three different police station terms here (metropolitan police department, etc). I kept getting them mixed up. Finally, I put in a synonym for ‘police’ for each of them. As an L2 learner, I’m ok with that for now.
For leech vocabulary, usually just spending some more time reviewing them (particularly by looking through all of the vocabulary composed of similar kanji) is enough to squash them. It’s really helpful to review the different ways a kanji can be pronounced and the ways its meaning can be altered or replaced.
#3 Less about leeches but more about keeping your queue low, I use the ignore script to ignore stupid errors like if I make a typo in Japanese or get the part of speech wrong for a kanji–it’s very easy to abuse though. And I do abuse it.
Feel free to share some leech pairs.