Mnemonics work when you don’t have much to grasp in terms of vocab or previous kanjis.
In my case I have been learning vocab side by side al along, so now I found many kanjis for which I already know words, so it’s like finally remembering the name of that guy / girl you know for sure you’ve met before 
…
Also there’s a great tool here (a script)
That after some hundred kanjis will allow you to see the logic among the kanjis that share components which are the largest part of all joujo kanji. So you can group kanjis, and make mnemonics for the group (which is far more efficient to me).
Mnemonics as presented in the website are currently something that it’s for the most part unnecessary if the above tools are available for any new kanji I’m learning.