I use both ConfusionGuesser (linked above) and [Userscript] Niai 似合い Visually Similar Kanji (adds a MUCH more detailed section to lesson pages and kanji pages with list of visually similar kanji) to try to help during lessons / reviews and for review just after failing an item during a review.
I also often use https://thekanjimap.com/ to pull up all kanji with a shared radical and then write them down and review them together, focus on the differentiating feature, and sometimes come up with my own extra mnemonics or borrow mnemonics from kanjidamage.com for trying to distinguish between similar kanji.
For example, a recent list:
- 憎（ぞう）hate (radical: left heart) “hate is a feeling in the heart”
- 増（ぞう）increase (radical: ground) “increase from the ground up”
- 僧（ぞう）monk (radical: person/leader) “monks are people, too”
- 層（そう）layer (radical: flag) “there’s a flag at the end of the level before Mario can get to the next layer” [this one is a little silly, but I actually don’t usually have trouble remembering 層 so it works]
- 贈（ぞう）gift/present (radical: shell/money) [haven’t actually learned this one yet, but the 貝 radical often means money so it won’t be too hard to remember]