Yes, it is correct that the Nafilah prayers can be performed while
sitting or walking. It can be done simply by reciting Surah Al Hamd
and optionally another Surah after it, which is not compulsory. Then
in the position of sitting, to bend for Ruku ; and then to bow for
Sujood. If it is being performed while walking, there is no
condition to face the Qiblah and the Rukoo' and the Sujood can be
performed by a slight bending of the head for Ruku and a little bit
more bending of the head for Sujood or even by bending the head or the eyes.