Helsinki is 5 hours ahead of Brasília
Best overlap: 8:00 AM to 1:00 PM in Brasília is 1:00 PM to 6:00 PM in Helsinki.
Both offices are open during 8:00 AM to 1:00 PM Brasília time, which is 1:00 PM to 6:00 PM in Helsinki. You've got a decent 5-hour window. Set a recurring time near 8:00 AM in Brasília (1:00 PM in Helsinki) and stick to it. Because only Helsinki changes its clocks, the overlap above isn't fixed; expect a one-hour shift when Helsinki enters or leaves daylight saving.