While doing some reading I found Mourão Filho's brainchild, the Cohen plan, which infamously gave Vargas a reason for his self-coup, was originally intended not as a forged communist plan but a thought experiment. It was originally signed "Bela Kun", but once Mourão Filho remembered another Integralist called Bela Kun "Bela Cohen", he scratched over the last name and wrote Cohen. His typist didn't understand and just left it as "Cohen", giving it the name. Plínio Salgado didn't like it but Mourão Filho left a copy with another military contact and it spread. When Vargas used the document Integralists did not protest as they already wanted a dictatorship anyways.
Part of Mourão's hastiness was because, without a promotion, he'd have to retire on the 9th of May. Indeed, he was promptly promoted after the rebel victory. His partner Guedes was about to be replaced.
The actual course of events was farcical. There was mostly inertia on both sides. Civilian and military legalists and rebels were on buildings across each other, in different levels of the same buildings or even in the same levels; many continued to carry out their bureaucratic work during and after the coup, and some "arrests" consisted of not being allowed to leave the building. Aside from the 7 dead civilians the only violence was in some verbal confrontations and jostles.

Some sources I'm using are isolated pieces of news, biographic summaries, brief military papers, a long study on Mourão Filho, a pro-rebel/revolutionary site which goes very in-depth no some topics and Gaspari's book. There is a primary source detailing the march from Minas Gerais to Rio de Janeiro but it isn't available anywhere on the Internet. Gaspari doesn't cover everything I want but it's a strong source and he was personally in contact with many of the key figures, which at times allows him to say that "he confirmed to me". He often gives precise hours for events.