Useful question. (Quảng Đức, the man on fire, was protesting the persecution of Buddhists):
I partially agree with SSSD answer. He says the shortest way is through anapana (respiration) style meditation. In standard ten-day vipassana meditation retreats, the first three days is spent learning/practicing anapana. The intention is on this to hone one's senses to accurately practice vipassana. That's what I came to understand its purpose at least. However, I believe--after experiencing reality beyond gross sensations--the quickest method is via vipassana started with anapana. (Anapana should be used as needed.)
A bonus effect vipassana students seem to experience, is the understanding of how physical pain is transient. In other words, it seems that most make a large step to achieving a state of non-reaction, stoic observation of pain.
For instance, after the course was over, one girl mentioned how she was taking a shower during the course. She decided to experiment. She turned the temperature all the way cold...then all the way hot. She observed the frigid liquid pouring over her without aversion. Then she observed the scalding hot water on her, unscathed. Two others noted they had done the same thing during the ten-day retreat.
My experience for truly understanding, at least temporarily, was on "vipassana day." I followed the rules of the grounds: Didn't observe the others during the course, was timely, etc. On the fourth day, after sitting for hours, I really wanted to move. My legs were in very uncomfortable pain. After ~34 hours of meditation (over the 3.5 days), I just kept observing my breathing as Goenkaji and the teacher instructed. Just before learning the vipassana (body scanning) technique, I had this "storm" of pain well up. Legs began to shake. But it was in those few moments, after learning vipassana, the pain...still present...was observed without reaction. My legs immediately went still.
In about four days (10 hours per day) of anapana and vipassana I did not achieve a complete state of physical suffering. I experienced the state. I sampled a sliver of the pie. I should also mention that I was practicing sitting leading up the course. And before sitting, I went through all the free guided exercises of the Headspace app. I like to be overprepared.
To give you a better sense of how long it might take, before taking the course, I had very poor meditation technique. Ha, it was atrocious. I was mixing methods and taking the easy way out (counting). I was doing that for at least two years, on and off, doing poorly executed self-taught methods. My point is that it's extremely beneficial to follow a formal meditation technique, and finding a teacher will further the value. Otherwise, a state of no physical suffering may not ever happen. (Regardless, the goal itself should not be a state of no physical suffering. It's a darn good reason to start though ;)
So we now know that it may never happen if following poor procedures. Second, one needs to consistently meditate every day. It doesn't necessarily have to be vipassana. One simply needs to sit, and ideally follow a formal technique.
How long until expert level? This does not mean one has achieved a state of no-self and the relinquishment of suffering, but it may give you a better idea of how long it might take. These are based off the 10k-hour rule-of-thumb:
Case 1: Full-Time Job
- 2000 hours per year (50 weeks per year, 40 hours per week)
Case 2: Part-time
Same deal, but 20 hours per week meditating. I made it 50 instead of 52 weeks to point out that it's not a cake walk: it does require concentrated effort...
- 1000 hours (part-time work-week) per year
Case 3: Good Student
Meditating the recommended hour in the morning and hour at night. They're such a good student.
Case 4: Adam's Original Plan
Case 5: Ain't Nobody Got Time Fo Dat
Could also knock off a year for every ten years if taking a ten-day (100 hour) course every year.