How did the Buddha subdue fear and terror while standing, sitting, etc.? The Bhaya Bherava Sutta (MN4) states the following:

...I stayed in the sort of places that are awe-inspiring and make your hair stand on end, such as park-shrines, forest-shrines, &amp; tree-shrines. And while I was staying there a wild animal would come, or a peacock would make a twig fall, or wind would rustle the fallen leaves. The thought would occur to me: 'Is this that fear &amp; terror coming?' Then the thought occurred to me: 'Why do I just keep waiting for fear?
What if I, in whatever state I'm in when fear &amp; terror come to me,
were to subdue that fear &amp; terror in that very state?' So when fear &amp;
terror came to me while I was walking back &amp; forth, I would not stand
or sit or lie down. I would keep walking back &amp; forth until I had
subdued that fear &amp; terror. When fear &amp; terror came to me while I was
standing, I would not walk or sit or lie down. I would keep standing
until I had subdued that fear &amp; terror. When fear &amp; terror came to me
while I was sitting, I would not lie down or stand up or walk. I would
keep sitting until I had subdued that fear &amp; terror. When fear &amp;
terror came to me while I was lying down, I would not sit up or stand
or walk. I would keep lying down until I had subdued that fear &amp;
terror.

However, it does not say how the Buddha subdued the fear and terror while standing, sitting, etc. How could a practitioner understand and use this method?
Buddha has given a detailed answer to handling fear and trepidation in the Sutta SN 11.3. Below I quote the relevant part:


  “But, bhikkhus, I say this: If you have gone to a forest or to the
  foot of a tree or to an empty hut, and fear or trepidation or terror
  should arise in you, on that occasion you should recollect me thus:
  ‘The Blessed One is an arahant, perfectly enlightened, accomplished in
  true knowledge and conduct, fortunate, knower of the world,
  unsurpassed leader of persons to be tamed, teacher of devas and
  humans, the Enlightened One, the Blessed One.’ For when you recollect
  me, bhikkhus, whatever fear or trepidation or terror you may have will
  be abandoned.
  
  “If you cannot recollect me, then you should recollect the Dhamma
  thus: ‘The Dhamma is well expounded by the Blessed One, directly
  visible, immediate, inviting one to come and see, applicable, to be
  personally experienced by the wise.’ For when you recollect the
  Dhamma, bhikkhus, whatever fear or trepidation or terror you may have
  will be abandoned.
  
  “If you cannot recollect the Dhamma, then you should recollect the
  Saṅgha thus: ‘The Saṅgha of the Blessed One’s disciples is practising
  the good way, practising the straight way, practising the true way,
  practising the proper way; that is, the four pairs of persons, the
  eight types of individuals—this Saṅgha of the Blessed One’s disciples
  is worthy of gifts, worthy of hospitality, worthy of offerings, worthy
  of reverential salutation, the unsurpassed field of merit for the
  world.’ For when you recollect the Saṅgha, bhikkhus, whatever fear or
  trepidation or terror you may have will be abandoned.


To answer the question How did the Buddha manage fear? I would say that he recalled Dhamma. If anyone recalls Dhamma, all the fear will vanish or fade away.