Śrī Matre Namaḥ

Per Guruji, Viraja Homa can be taken on as a standalone practice.

Burning karmas though sadhana:
Any sadhana can help "burn" our karmas. We are composed of three bodies: gross, subtle and causal which we identify with. Your karmas and past impressions are housed in causal body. One of the main ideas of worship is to go beyond one's limitations and attain full identity with the chosen Deity. When the union with the Divine is reached, the attachment to one's identity and body ceases to exist along with one's karmas.

Viraja Homa is an example of such practice. Below is what Guruji says about it:

Of course, you realize that—as a human being still trying to overcome the sense of multiplicity constantly streaming in through your five senses—you are in a very limited state of being. How do you overcome this state? By resetting your self-perception to a state in which you are the Goddess.

By performing this practice…

…you proceed to reset yourself to this state—getting rid of this old, useless, stupid, worrisome kind of existence you’re going through.

The end result:

You create all this through the power of your imagination and creativity, the acuteness of your visualization, the clarity of your perception—using all of these skills, you create an image, and this image goes and does whatever good it can. The world you create is every bit as real as the life in which you believe your individual self to exist right now. It is just like a child born from you—it will eventually continue its existence independently of you. Thus do you go about creating an immortal body for yourself.

Source: "Goddess and the Guru"