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).
An unsupported shoulder stand assumes your regular shoulder stand is stable and comfortable. if your feeling any stress on your neck then you should probably avoid the unsupported version for the time being.
A good warm up is often required to allow the shoulders to relax enough for unsupported shoulder stand, the and arm variations in Tadasana from Day1 are a good place to start, these could also be done in dandasana.
Practicing forward folding postures with the chin down will also stretch and relax the neck in preparation for shoulder stands as would engaging jalandhara bandha (chin lock).
Explore the unsupported headstand by removing one hand at a time from supporting your back may be a good introduction to finding the required balance.
In regular shoulderstand, stretch your back more, extend up through the legs and lean your torso and hips in the direction of your head, your legs will come beyond your head but remain straight up.
Your hands on your back should feel as if they are hardly necessary to support the shoulder stand.
Reach up with on arm on the inhalation and stretch it up along your thigh, remain for three breaths. Return it to your back and repeat with the other hand, remembering to stretch your hand up along the thigh, stretching through your trunk and the full length of your legs feet and toes.
If one hand at a time is comfortable, take first one hand off the back, stretch it along the thighs and then after a breath bring the other hand to the other thigh. Hold for a breath and then bring the first hand back to the back and after another breath return the second hand.
When comfortable in niralumaba sarvangasana (unsupported headstand) consider exploring the vinyasas.
When lowering and raising the leg, begin the action in the hip, while stretching through the length of the leg.
By lowering on the inhalation you keep more control of the descent.
In lowering the leg to the mat (pic.3) place one arm on the mat above your head on the inhalation, stay for a breath and then on the next inhalation lower the leg to the palm, hold the toe and ideally stay for three breaths.
You may wish to lower the leg on the inhalation and raise it on the exhalation while you become comfortable with the movement and shift in balance, repeating three times and then holding the toes on the third lowering.
Problems can come on the raising of the leg back up to horizontal. be sure to keep the torso forward and stretching up through the legs and keeping the the trailing leg forward of your head while raising the leg.
in the next vinyasa bring both hands above the head. in the beginning you might lower first one hand, stay for a breath and then bring the other to join it staying for a breath before returning the first hand on the next breath and the second hand on the following breath.
As this becomes comfortable and stable try bringing both hands above the head and stay for three breaths.
There is another vinyasa not shown, where you bring you arms behind your head clasping your elbows.
In the vinyasa in picture six, halasana (plough) lay the hands along the mat behind your head and then on the inhalation lower your legs to the mat above your head, the stretched out arms give more stability in this posture.