As a reminder, Ramaswami recommends we spend five minutes in Sarvangasana (first three minutes with the legs relaxed next two with the legs straight in standard Shoulderstand) before practising the sarvangasana vinyasas
Ramaswami would also recommend a counterpose after sarvangasana so as to relieve the strain placed on the neck and shoulders, he suggests bhujangasana (cobra, Day 45) and especially makrasana (crocodile, Day 44) as ideal counterposes, stating that, 'The counterposes, as a rule, should be simple, effective and targeted' (Yoga beneath the surface p105).
To be able to bring the knees to the mat beside your ears, the neck and shoulders need to be sufficiently relaxed. A long sarvangasana or some halasana subroutine variations can help achieve this,
Engage jalandhara bandha, the chin lock, bringing the chin tight against the chest.
Engage uddiyana bandha, drawing the belly in and up to creat more space for the forward fold.
Kandapindasana is a posture in which we can stay for a considerable amount of time, Ramaswami recommends twelve breaths.
Because of the tight fold, the inhalation will be short but try to lengthen the exhalation.
To bring your legs through the arms, retain uddiyana and on the inhalation, stretching each vertebra, allow your back to slowly unfurl along the mat, keeping your legs as close to your body as possible all the way through the arms.
Ideally the legs should not touch the arms on the way through.