the most efficient way to brush up technicals to prepare for case studies?

Hi, I'm interested in (literally and seriously) any investing job as long as it's related to dealing with shares or something that could change to shares such as bonds and debts. So basically I'm open to any ECM, DCM, LevFin, ER, IBD, PM, and whatsoever FO role at IB, PE, and HF, all of which you professionals will be more familiar with and aware of than I.

I studied math, econ, and philosophy at a non-target LAC, where no finance course other than introductory accounting one is offered, and self-taught for a month to pass CFA 1 several years ago (I know it's a joke but am just letting you know that my financial knowledge is slightly better than nothing).

I was a little embarrassed finding that not only are IBD but ER entrance-level candidates these days asked seemingly difficult technical questions like filling in blanks on financial statements, which I've totally forgotten for being away from finance matters for almost 6 years.

What would be the best and fastest way to brush up financial knowledge for entrance-level(i.e., fresh college graduate) technical interviews for ER and IBD, if my interests must be narrowed down?

Reviewing my CFA I materials?
Analyzing financial statements of XYZ firms referring to some case study examples on Google?
WSO online courses? (WOULDN'T TAKE WSO BOT's OPINION HERE NO MATTER HOW VALID)

Any suggestion or advice EITHER

on my current way-too-complicated situation: https://www.wallstreetoasis.com/forum/hedge-fund/…

OR on my recently revised resume will also be appreciated.

Thanks in advance,
from old newbie :)