Please don't waste your time with "Case In Point", at least not with the case cracking section -> the ~15 frameworks given are overly specific, not MECE, and you won't be able to reuse them. Victor Cheng's material is much better (a good starting point are his ~6 hours of free YouTube videos btw).
As for hiring a coach... up to you obviously, but remember that the field is extremely competitive (there are literally dozens of qualified applicants for every open spot) and the financial and professional upsides are phenomenal.
Whatever you decide though, make sure to start the actual prep long before you apply. It takes most of us well over 100 hours of focused, dedicated prep time to figure out this case thingy. I prepped after my MBA but didn't know what I was supposed to do, and went nowhere. Years later, I prepped again and made it - but that second time, I had the benefit of a few BCG friends giving me personalized feedback + leveraged Victor Cheng's material enormously. PrepLounge didn't exist then, or I would have used it as well. In spite of all of this, I studied for ~120 hours that second time again. No way I'd have been ready if I had waited until I applied to prepare myself.
PS: Let's say you hire a coach & spend significant time to prepare, but don't get an interview. Did you waste this money and time? I'd argue no actually, these skills will be reusable in other interviews (many former consultants in every industry, they will pretty much all give you a case or test your thought process) and even in your future job (can you be hypothesis driven?)
tl;dr: You can succeed without a coach, but (1) it takes a lot of time, and (2) the field is so competitive that I recommend you let others help you when possible. Even if it doesn't work, that case cracking skill will be useful to you later in other interviews and 'real jobs'