So, I applied for Brazil visa at the Brazil Consulate in San Francisco.. The process is very straight forward. The consulate is very helpful, welcoming and timely. I would think using a visa agent won't provide any great advantage.
0) Get an appointment from the website (this gets you a appointment time for visiting the Consulate).
1) Needed: 1 passport size photo, pre filled form.
2) USPS Money order for required fees addressed to Consulate General of Brazil (fees for Indian citizen, 20$, for US 130 $).
2) Passport with 6 months validity
3) Return tickets/Itinerary (I just took them to be sure, the website doesn't mention this to be required).
4) For getting the Passport returned by mail, use Express mail from USPS. (costed 17$).
The application process took about 30 minutes in total. The visa took about 10 business days, my passport was returned duly is about 12 business days including delivery time. I choose to get the passport delivered as I didn't want to travel to San Francisco again.
BTW, when the consulate mentions they will only process 42(or whatever) applications per day it doesn't mean that you may or may not be able to apply visa that they if you get the appointment if means that you are in those 42 applications.