...since (some forms) Buddhism uses vipassana and shamatha to attain enlightenment and liberation (also Nirvana) Gnosticism uses (insert method here) to attain enlightenment and liberation (also called Gnosis). ...does the EG teach a specific method to allow the user to obtain enlightenment, or in this case, Gnosis?It is a mistake to simply equate Gnosis with enlightenment. Gnosis is the method/means of liberation, not the liberated state. The state of redemption or liberation would be more equivalent to the enlightened state. The one who is liberated has Gnosis, it being the means of liberation, and the texts use it in that way as well, but it is not the only way that the term is used.
In short, Gnosis is not in itself a state of being (though you can use it to indirectly refer to that), it is a way to refer to a fundamental spiritual growth/transformation/liberation process.
The methods for progressing in Gnosis that are referred to in ancient scriptures, and that we use today in the EG, are richly poetic and symbolic forms of personal transformational experiences that are either focused upon an individual or are generally participated in by a group. They produce changes in consciousness, and have both initiatory (pivotal) transformative effects, and also gradual transformative effects from regular participation (such as meditation has).
They involve participating in the sacred stories (myths) of the tradition and applying them directly to yourself through having a form to experience them in, so one can gain gnosis of them. In our practice, many aspects of these are revisited every year. There are also times in one's life when there is a more direct need/use of a deeper application/experience of some of them. And there are traditional methods for this as well.
One can also go through a long process of learning how to offer these methods in service to others, which involves participation at gradually higher levels of responsibility, while undergoing a further transformative process. They are not something you can try on your own without training and experience.
These methods are what we do as a church. They are richly symbolic liturgical services, that primarily consist of the mysteries/sacraments that are listed in the Gospel of Philip. The regular transformational method we use is the Holy Gnostic Eucharist. The methods we employ as a church are the mysteries/sacraments and other liturgical rituals.
I know Christian churches generally use striped-down versions of the sacraments and largely understand them in a theological manner that is quite different from their origin as mystery practices in the ancient world. But that is not our approach. We take care to follow the traditional forms and traditional requirements for conveying the mysteries. And, in my own experience and experiences of others reported to me—these forms serve that purpose. And that is the purpose and function of the EG as a church. It isn't that we hold services and then do the real transformational work later on, the services are real transformational methods—our services are public group spiritual practice.
Individual spiritual practice is also encouraged. Contemplation, prayer, meditation, active imagination, and dream work, are among practices commonly used by individuals in our tradition. Education in the tradition and related topics is also a part of our ministry through the Gnostic Society. All of these activities fit under the ancient understanding of spiritual exercises and aid our personal development, as well as preparation and integration of the mysteries. Yet, the spiritual practices that are more oriented towards attaining Gnosis are the mysteries instituted by Christ.