They can keep saying let Bible should interprete itself but we know they don't follow that mantra
You are correct. Here are some of their tricks:
1. They take a verse like Romans 6: 7 out of context and use it to deny the purpose of Jesus sacrifice.
2. They go back to the Old Testament and find a scripture that suits their purposes, then use it to override an established NT doctrine.
3. When they run accross a NT scripture that proves their new doctine to be wrong, they give it a symbolic spin and say it's not meant to be understood literally.
I believe that WT literature is specifically designed to innoculate people against receiving the 'simplicity of Christ".
2 Cor. 11:3 But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ.
I was pretty much an atheist for around 8 years after leaving. As I began to understand the depth of various deceptions, I got to wondering why would anyone put forth so much complicated effort to obscure the biblical narrative, unless there was something to it.