The Brazilian Embassy web site suggests that a tourist visa can take up to fifteen days to process. It also says
Whether applying in person, by post, through a visa agency and/or
courier service, visas will be processed in the order of arrival. The
Embassy does not provide urgent or priority services, and as such no
expediting fees are incurred by the Embassy.
Agencies and courier services will not be able to help. The web site has this to say:
The Embassy of Brazil in Canberra is not affiliated with nor does it
endorse any visa agencies and/or courier services. All such agencies
receive identical treatment by the Embassy's Consular section.
At best you can lodge documents in person in Canberra or Sydney, for which you will need an appointment, bookable through the web site.
I speculate that a straightforward application with all required documentation (checklist on the web site) might be processed faster than fifteen days, but I doubt you could get anyone to commit to that.
There is no telephone support for visas at the Brazilian embassy or consulate, so you'll be limited to their turnaround times for email if you want to ask questions ahead of time.