I have a new T-Rex 450SE V2 that I am currently building. Everything that I have read says to completely disassembly all the pre-assembled metal parts to check for the presents of thread-lock. I understand the importance of this, however, my question is, can I put more thread-lock on the same screw that had thread lock on it before? Do I need to do any cleaning first? If so how?

It is highly recommended to clean the threads before you apply new threadlocking compound. I use a small wire brush to clean the threads prior to using fresh threadlock. I am sure that other people have other methods, but that works very well.

Hope that helps.