First off I'd like to address what you wrote last, about keeping scripture above the writings of EGW. The Bible, and the Bible only, is our standard; the writings of EGW act more as a magnifying glass. It is the Bible that creates and supports our doctrines, not the writings of EGW. If I need EGW writings to support my beliefs, and not the Bible, then I'm in the wrong denomination, right? You see, this is why, in America at least, SDAs are often referred to as being a 'cult'. When fellow SDAs treat EGW's writings as being equal to the Bible, and witness according to her writings, that paints a bad picture and makes it appear that Ellen is our God - and that is "cult-like" behaviour. This should never NEVER be the case! While I do not disown her writings, for I believe them to truly be inspired writings that lead to greter understanding of the scriptures, I never place them equal to or above the Holy Bible.
And yes, I believe it is fully possible that our faith, beliefs, and doctrines can be fully defended with the Bible only. As you've seen from my essays, I can take any of our docturnal beliefs, and use nothing but scripture, firmly establish our perspective of the truth with them. In fact, it is the Bible that is used to determine if EGW was in fact a messenger of God or not - not the other way around as many have claimed we do.
As to the question about
when do I introduce EGW to people that I'm witnessing to - that's an easy one. I tell them right up front when I show them the 28 fundamental beliefs we have. I don't hide her. But, just as EGW herself says, do not give her writings any credibility at all until your are FIRST firmly rooted in the teachings of the Bible. So, after much much study, that is when I'd re-introduce her writings - to amplify what the Bible has already taught. So the short answer is I do it first and last.