Just because Gandhamādana states that reciting ‘Hanuman’ itself is a sacred bath, it does not imply that a person should skip his daily mandatory bath just because he performs nama japa. Bathing is pre-requisite for cleansing the physical body. Reciting the name of Hanuman is a sacred mental bath.
The term ‘upāsana’ means visualizing the favorite deity in every deed performed in the daily life.
There are millions of Devatas. Each Devata has millions of mantras associated with Him/Her. If so, how is a person to choose which mantra is supposedly superior? To a person, that mantra into which he has received initiation from his Guru is the most superior mantra. Based on the individual destiny, buddhi (intellect) and mental tendencies (nature) of the person, the spiritual Self-realized Guru will bless the devotee with a particular mantra. Such mantra should become the most superior mantra for the person.
There are some who do not see the necessity of securing a spiritual Guru or initiation into a mantra from a spiritual Guru. They believe that locating mantras in books and reciting them is good enough. Fine. In this case, it will be apt if you consider the holy book as your Guru and treat the mantra as initiation from that Guru. Those who have not found a Guru can treat the sound of the mantra that they have heard as a Guru and meditate upon it. Suppose your neighbour is listening to a TV programme and the mantra ‘Sita rāmābhyām namaḥ’ falls into your ears, treat that itself as an initiation and focus on that mantra.
Mantra thus received from the Guru should be treated as the most supreme mantra and hence it should be recollected and recited at all times! This is ‘upāsana’ of the mantra. There is a very sacred hymn ‘sandhyā vandana bhadramastu’ wherein the poet very marvelously states- ‘I offer my obeisance to all these obligatory duties of bathing, sandhya vandana etc. However to me undertaking the japa of Lord Krishna’s name is of utmost importance.’
Om namo Hanumate namaha.