OSCP can be considered entry-level pen testing cert but is the most difficult entry level cert compare others entry level cert eg. ccna ..
Enumeration need to base on experience and patient .
Deep dive in linux and windows privilege escalation .
Lastly you need to know how and what to modify exploit code once you found the vulnerability .
GOOGLE , GITHUB , ExploitDB is your best friend .
As for BoF pretty straight forward in OSCP exam..not much challenge . Just practice the exercise and understand the concept will do .( you need to understand how to modify the code base on the input )
Anyway OSCP just like HTB or CTF ..... dont expect you get OSCP then know to do PTVA . You cant capture the flag in customer environment ,haha !
I will recommend eLearnSecurity eJPT > eCCPT > OSCP .
Start with eJPT ,eCCPT first if you are not experienced enough.
The OSCP book&videos are horrible and the course has a pretty steep learning curve.
Personally i feel eLearnSecurity can learn more knowledge but the Name not recognize by HR.