Most JWs - myself ( as an now ex ) included - just have a pretty superficial knowledge of the bible. It is anchored on the basic Society principles of "obey the slave" and "go out and preach". It's basically a kind of kindergarten level. Remember - JWs are actively told not to do any external research or to learn any hebrew or greek.
I remember an elder asked me to accompany him on a return visit he had on a guy who was a 20 year old theology student. We discussed things like the early history of the church in the NT and the trinity. Both of us thought we "knew our bibles" but the guy totally tore us apart - showed scriptures and used reasoning that we had never come across.
The Society quotes we used ( eg from the early Christians ) were shown to be pulled out of context or embellished. 80 combined years of attending meetings between us counted for nothing - we were left furtively looking up the concordance at the back of our bibles trying to make a defence. It really brought home to me just how little we actually knew and was a big "eureka" moment in me realising that this wasn't the truth.