Useful Mnemonics?

I've always been particulary annoyed by the 笔 as the simplification of 筆. Apparently the thinking was because the simplified character is like 毛 in the compound 毛笔. What kind of idiotic simplification of the original is that? I had forgotten 凭 as the simplification of 憑, apparently because of the compound 任凭. It's not as if 笔 or 凭 never appear outside of those two compounds. I guess the author of these simplifications thought that this would help to remember them. And on reflection, maybe they are useful mnemonics.