A few of the things I do are still grammar based even though I don't explain the grammar. Those fall into my gray area, for example trying to work with singular/plurals. Or trying to work with anything for that matter. There are things I still feel I need to 'teach' but I haven't worked out how to do it all yet. My biggest issues deal with fundamentals or fundamental chunks. I deal with them isolated right now and it seems very grammar-like to me. The matrix-less instruction deals more with putting those together to form more complex sentences without grammar. I'm finding with no grammar explanation in the begin (gray or not) the students take the second part much better without grammar and understand better than the grammar groups.
When I learned Japanese, I found the grammar explanation so confusing that I just stopped bothering with grammar. I later decided to teach how I learned. Now, I was in Japan so I had a lot more input than L2 learners but I still think it's the best way to learn either way. That may not be true for languages where the grammar is similar. And maybe not even true in Japan...
It's just what works for me.
Well, it actually started like emily said. I know the young students are going to get 6-10 years of grammar and relatively no speaking. I decided to counter balance that, I was going to do the opposite to ready the students for an all grammar school system. However, I found they made equal progress to the school system in a third of the time and mostly without homework. They seem to understand better, be able to use the language better and retention was higher. Their writing ability is very poor but that's an issue with time here. I only see them once a week for an hour and just can't afford to waste time writing. We later go back and do writing. They also get to write more than they ever wanted to in JHS and HS.
Sometimes I just have to teach grammar-translation because I work in Japan and my JHS and SHS students are going to have to know it, not English, for the their tests. Some of my adult students expect it. It's much easier to teach grammar but the reason I'd like to go the other way is that it appears to be better in the long run for my students.