Q: Is dhyAna a meditation technique?
R: dhyAna is not a 'technique' of meditation
dhyAna means meditation.
Q: dhAraNA is
concentration, with techniques, which naturally leads to dhyAna (true meditation or merging)
When you say that "true meditation" is merging, what is to merge with what?
The word "merging" implies the presence of two things. Are there two things at all? -- advaita teaching tells us that "What IS" is all One only. Two separate 'things' are not there.
From this advaita understanding we can deduce that the sense of a separate I, a separate "me" being present, is an imagination. It does not really exist. This imagined separation has to merge with "What IS." In other words, the imagination has to end. Hence it is ending the sense of separation, not a question of merger.
Ending the sense of separation, thus, does not mean investing any effort to change "What IS". Meditation does not require any effort to exclude something using the practice of concentration as a technique. (The practice of concentration implies preferring the presence of one thing to the exclusion of all other things).
Therefore, ending the sense of separation cannot come through concentration.
Hence dhyAna or meditation is merely "dropping" the false notion of a separate "me", separate from "What All IS."
If "What IS" is a fluctuation, I do not have to change/suppress/ modify the fluctuation. In fact, it cannot be done! For, there is nothing else other than the fluctuation at that moment. That's "What IS."
If What IS is deep sleep, "It" is deep sleep. If "What IS" is awake world, "It" is the awake world.
Q: Does it not mean that we are all indeed successful yogis every night when we sleep!
Yes, but, remember, there is no "we" in deep sleep.
As advaita says, "I am eternally "unchanging" and ever the same."
Then how can I be something 'different' any other time?
As advaita says: "It is only a false imagination to think that you are different or a separate person when you are awake."
So I am also the undivided totality of the entire wakeful world - the oneness of all the perceptions, sensations, and 'thoughts.'
(Thoughts are not excluded you see!).
The position is just like in the deep sleep. I am the entire "Whatever IS", in the deep sleep.
I am the entire What IS in the awake state.
Q: My question to you is have you ever had an extended period without thought? If so what was your experience?
In the light of the above explanation, it is easy to find the answer to the two questions.
Unless I consciously "separate" myself in order to place a "me" at a distance from "What All IS," why would I have to wrestle with thoughts in the awake world? As we said above the "What IS All" includes the thoughts also.
I have not tried any "gimmicks" towards that end of perceiving a world and feeling sensations but stilling the thoughts exclusively - i.e. experience the perceptions of the world, sensations of the body but be thoughtless.
I try, instead, to be conscious of a separate "me" arising.
That is to say, I keep a watch if the thought "I am separate" or its kind arises.
If a thought of a separate "me" arises, the best thing (or perhaps the only thing) to be done is to just 'notice' it.
Having any 'agenda' with it to change or suppress the 'thought' will go only to strengthen it! That would be counterproductive.
Hope I am able to respond to your query.