One of my friends was a JW for years as a youth, and his brother is yet today a "vested" honorable elder, having worked for free for four years at their printing plant in NYC...[ the largest in the world, I believe..] I talked to him a lot about their methods.
I have witnessed to them as they have approached me , over the years, and I think I have some helpful experience in these issues.
They are trained to respond as you rebut their arguements, especially from scripture that endorses Jesus as God ....the Creator, [ Which He undoubtedly is..]
The Lord gave me this strategy; I gave them my testimony, and refused to budge off of it....It went like this...
" I lived in debauchery and filth, and when I called out to Jesus, begging forgiveness for my wickedness, I was answered with a Spirit that descended into my body." [ I did this on a street corner, on my knees , in Boulder Colorado in March of 1972..]
"Instantly I experienced every sin I had ever done leave me, like a foul laundry bag. Real Love filled me, for the very first time ever, and Peace flooded me too. I was brand new, another person than I was before that moment...I was changed by this Spirit!"
This spirit that entered me is still with me today, and it is the gift that Jesus promised that He would give when He went to the Father....The very same gift He gave at Pentecost in the Bible that Peter preached about.
Remember that He said; Marvel not that I say unto you that you MUST be born again to see the Kingdom of Heaven?" I was born again that day, and He has spoken to me many, many times since then, in many ways.
That Spirit illuminated the Bible for the very first time...it was just a cold hammer to me before that day....and now it feeds me every day of my life, and bears witness completly with thae Spirit in me, that Jesus promised those that believe. I know He is God and Jehovah, because I know Him."
They overcame him by the Blood of the Lamb, and the WORD of their TESTIMONY, and did not love their own lives even unto their death.
I try to testify to them seeking to impact them as the Spirit leads....for only He can convict them, or save them. I try to love them, but make a difference in some. I've seen honost seekers in the JW ranks, that sincerely believe they are following God's path, and I've seen real nasty wolves who enjoy their evil control over the innocent.
We must use discernment, and be gentle and loving, and attempt to minister to them out of love. Some of the seeds sewn may take years to grow up, but don't despair. If spoken in the Spirit, God's word will not return unto Him void; even warnings.
Remember, they have not been born again, and cannot respond to Him in your testimony, but they love to wrangle over scripture and words. They must be saved, or perish.