Converting your licence would be a test of patience, but the process itself isn't too difficult. Normally you would sit the Brazilian PPL exams and possibly do a check ride, (you will need Portuguese for the tests) but that's about it.
Importing your Pitts is not going to be fun
You can expect to pay duties in the range of 60-90%, and you will need to place the aircraft on the Brazilian register. Expect a lot of headaches and a lot of expense trying to do that, so realistically it would be better to sell your Pitts there and try to find one on the local market.
However, are you a citizen or do you have a residence visa?
AFAIK if you don't have a CPF (individual tax number) you won't be able to exchange your licence or import your aircraft. As a visitor you can fly on your US/UK PPL, without the need to convert it, most aeroclubes will only ask that you do a check ride before renting you an aircraft.
GA is alive and well in Brazil, the aeroclubes are normally very helpful and very knowledgeable, so I would follow up the earlier advice to get in contact with one and ask them the same questions. They would certainly have up to date information for you.
Good luck