I'm sure there is a teaching somewhere that explains his experiences under the bodhi tree post buddhahood, but he certainly did not need to sustain a fabricated state with effort or anything of that nature. As I wrote before on here: One of the characteristics of nirvana is that it is "permanent" because it is defined as a total cessation of cause for rebirth in the three realms. Since there is no possibility of cause for "re-arising" nirvana is said to be "permanent." Buddhahood is irreversible and permanent. Nirvāṇa is the total exhaustion of one's ignorance regarding the nature of phenomena, and for that reason nirvāṇa is described as a cessation. What ceases is the cause for the further arising and proliferation of delusion regarding the nature of phenomena, which is precisely the cessation of cause for the arising of the cyclical round of rebirth in the three realms we call "saṃsāra." For this reason, nirvāṇa is said to be 'permanent', because due to the exhaustion of cause for the further proliferation of saṃsāra, saṃsāra no longer has any way to arise. Tsele Natsok Rangdrol: You might ask, 'Why wouldn't confusion reoccur as before, after... [liberation has occured]?" This is because no basis [foundation] exists for its re-arising. Samantabhadra's liberation into the basis [wisdom] itself and the yogi liberated through practicing the path are both devoid of any basis [foundation] for reverting back to becoming a cause, just like a person who has recovered from a plague or the fruit of the se tree. He then states that the se tree is a particular tree which is poisonous to touch, causing blisters and swelling. However once recovered, one is then immune. Lopon Tenzin Namdak also explains this principle of immunity: Anyone who follows the teachings of the Buddhas will most likely attain results and purify negative karmic causes. Then that person will be like a man who has caught smallpox in the past; he will never catch it again because he is immune. The sickness of samsara will never come back. And this is the purpose of following the teachings. and from Lopon Kunga Namdrol: Buddhahood is a subtractive process; it means removing, gradually, obscurations of affliction and obscurations of knowledge. Since wisdom burns these obscurations away, in the end they have no causes for returning; and further, the causes for buddhahood are permanent leading to a permanent result.

I'm sure there is a teaching somewhere that explains his experiences under the bodhi tree post buddhahood, but he certainly did not need to sustain a fabricated state with effort or anything of that nature.

As I wrote before on here:

One of the characteristics of nirvana is that it is "permanent" because it is defined as a total cessation of cause for rebirth in the three realms. Since there is no possibility of cause for "re-arising" nirvana is said to be "permanent."

Buddhahood is irreversible and permanent. Nirvāṇa is the total exhaustion of one's ignorance regarding the nature of phenomena, and for that reason nirvāṇa is described as a cessation. What ceases is the cause for the further arising and proliferation of delusion regarding the nature of phenomena, which is precisely the cessation of cause for the arising of the cyclical round of rebirth in the three realms we call "saṃsāra."

For this reason, nirvāṇa is said to be 'permanent', because due to the exhaustion of cause for the further proliferation of saṃsāra, saṃsāra no longer has any way to arise.

Tsele Natsok Rangdrol:

You might ask, 'Why wouldn't confusion reoccur as before, after... [liberation has occured]?" This is because no basis [foundation] exists for its re-arising. Samantabhadra's liberation into the basis [wisdom] itself and the yogi liberated through practicing the path are both devoid of any basis [foundation] for reverting back to becoming a cause, just like a person who has recovered from a plague or the fruit of the se tree.

He then states that the se tree is a particular tree which is poisonous to touch, causing blisters and swelling. However once recovered, one is then immune.

Lopon Tenzin Namdak also explains this principle of immunity:

Anyone who follows the teachings of the Buddhas will most likely attain results and purify negative karmic causes. Then that person will be like a man who has caught smallpox in the past; he will never catch it again because he is immune. The sickness of samsara will never come back. And this is the purpose of following the teachings.

and from Lopon Kunga Namdrol:

Buddhahood is a subtractive process; it means removing, gradually, obscurations of affliction and obscurations of knowledge. Since wisdom burns these obscurations away, in the end they have no causes for returning; and further, the causes for buddhahood are permanent leading to a permanent result.