The advice of the Paramacharya of Kanchi Kamakoti Peetham should be carefully heeded in this respect -
As this Vidya is the means of both Bhoga and Moksha, it is taught secretly only to eligible persons. The practitioner is also enjoined to keep this Upasana secret. The Sruti says:
अन्तः शाक्तः | बहिश्शैवः | लोके वैष्णवः || [कौलोपनिषत्]
AntaH shAktaH bahiH shaivaH loke vaiShNavaH (Kaulopanishad)
Ar heart Shakta, outwardly a Shaiva and in gatherings a Vaishnava (who generally gather together for worshipping in the praise of Hari)
The Shakti Upasana should be known only to the mind and not broadcast. Even while wearing on the forehead the Sindura Prasadam of Devi, the Upasaka should cover it with bhasma. As Shiva and Shakti are one, this can be done.
aIyate shivasAyujyaM kShIyate pAshabandhanam
atha dIkSheti kathitaM budhaiH sacChAstravedibhiH ..
The first qualification for a Upasaka to perform Pooja is obtaining Diksha from a competent Guru. the rite called Diksha is supposed to be destroying all the limiting factors of the individual self and facilitate his union with Shiva.
Such a Initiator or Guru would advise his/her disciple if one is ready to chant these Shlokas or mantras even during impure time or otherwise and generally devotees are advised to take caution to the various rules according to the Shastras. Muruganar would not have stopped performing his rituals and Shardha specially, if it were advised by anybody else but Bhagavan.
The practice of Bhakti in all its three forms constitutes Upasana. There the form to be adopted as the object of devotion is also a matter of choice. Indeed, Bhagavan Krishna assures us that he confers on the sincere devotee, unwavering devotion to the chosen form.
YatrAsti bhogo na tatra mokShaH yatrAsti mokShaH na tu tatra bhogaH |
ShrIsundarI sAdhakapuMgavAnAM bhogashcha mokshashcha karastha eva ||
"Where there is worldly enjoyment, there is no salvation; where there is salvation, there is no worldly enjoyment. For the great worshippers of Sri Sundari, both worldly enjoyment and salvation are at hand’ – will come alive with a new significance."
Bhaskaraya has said:
The Sadhaka will experience, as his Japa and Upasana progress, that he is able to get some supernatural powers, Siddhis as they are known. His mind will also be distracted by various material pleasures thrusting themselves upon him. He must be careful, remembering parokShapriya hi devaH and these are directed at preventing him from attaining his goal of Brahma Jnana.
Salutations to Bhagavan