Over the years, I have taught many classes I used a speaking and listening technique. I do not teach reading as well as writing. I introduce a new language by listening and all lessons consist of speaking and listening only. I teach grammar simply through situations with no reference to grammar rules at all.
Thinking in a foreign language from an early stage helps students gain a level of fluency making very few errors in communication.
I often find myself thinking in Polish and English, flying back and forth from the two languages.
It is difficult to manage in two languages simultaneously. Anyhow, why would you like to?
I believe, the sooner a student learns to think in a foreign language, the faster she/he will learn. This can only take place if no reference at all is made to L1. They must be free from the interference of L1.
Maybe I am wrong?
On the other hand, I know that anyone who is learning a second language wishes and dreams about thinking in that language.
Time is always an issue for me.