The not and the kanji not are the same thing! That makes it easy... Not!
To remember ふ we'll use the word "fool."
Think of those jokes, where someone says something, then ends with a loud "NOTTTT!" Someone is doing that to you, over and over. What is that person? That person is a fool (ふ).
Currently there are no similar looking kanji which exist in the WaniKani learning system