>>108647
The purpose of pranayama is clearing your nadis, particularly ida, pingala and sushumna. There are no particular pranayama techniques for shapeshifting. You might experience bodily transformations brought about by this and by subsequent mastering vayu tattva, which is connected to the practice, and it can make other transformations occur easier but by itself it won't make you a shapeshifter. You might combine it with visualization and one-pointed awareness though.
So yeah, nadi shuddhi basically.
Here is the technique from Goraksasataka
Suddhim eti yada sarvam nadicakram maldkulam
Tadaiva jayate yogi prana samgrahane ksamah.
95. When the whole group of nadis, full of secretions, is purified, then indeed the Yogi
becomes capable of restraining the prana.
Baddhapadmasano yogi pranam candrena purayet.
Dharayitva yathaiakti bhuyah suryena recayet.
96. Assuming the lotus posture, the Yogi should fill in the prana through the left nostril; then,
having held it as long as possible, he should expel it through the right nostril.
Amrtam dadhisankasam goksirarajatopamam
Dhyatva candramaso bimbam prandyami sukhibhavet.
97. Having meditated on the circular image of the moon, nectar as white as curds (and) cow's
milk, (or) of the colour of purest silver, one practising pranayama should find peace.
Daksino svasamikrsya purayet udaram sanaih.
Kumbhayitva vidhanena praicandrena recayet
98. Having filled in the breath through the right nostril, one should fill the abdomen slowly;
having held it according to the rules he should expel (it slowly) through the left nostril.
Prajvalajjvalanajvalapunjamadityamandalam
Dhyatva njbhisthitam yogi prandytimi sukhibhavet.
99. Having meditated on the circle of the sun, full of a mass of flame of fire burning very
brightly in the navel, the Yogi who practices pranayama should find peace.
Pranam codidayd pibet parimitam bhuyo nyayarecayet.
Pitva pingalaya samiranamatho badhva tyajet vamaya.
Suryacandramasoranena vidhina bimbadvayam dhyayatah.
Suddha nadiganabhavanti yamino masatrayadurdhvatah.
100. Meditating in turn on the two images, moon and sun, (Yogi) should draw in the
breath through the left nostril; he should expel it again through the other, according to the
limit (of the times already explained): then having drawn in the breath through the right
nostril, and having held it, he should expel it through the left nostril. After three months
the group of nadis of the practicer becomes pure.
Yathiestham dharanam vayoranalasya pradipanam
Nadabhivyaktirarogyam jayate nadisodhanat.
101. By cleansing the nadis the prana (is) restrained as desired, the digestive fire (is)
kindled, internal sound is heard (becomes manifest), (and) one becomes diseaseless.
This is connected to the Tantrik symbolism that equals Moon with ida and Sun with pingala. Also, moon is connected with amrita -
the so called "nectar of immortality". Here is a similar technique from a different tradition, but without the visualization:
http://www.meditationexpert.com/meditation-techniques/m_9_step_bottled_wind_pranayama_practice.html
http://www.meditationexpert.com/meditation-techniques/m_nine_bottled_wind_kumbhaka_pranayama_breathing_techniques.htm