Qualification needed for UK citizen to teach in Brazil University?

What is your discipline? If you are in the sciences/medicine, the first step is to create an alliance with senior faculty members in a number of Universities by contacting them directly and letting them know what you are offering. You may have to visit and have an assessment and then they will decide if you meet an area of need. If you are are a young PhD, taking a one year Post Doc would be your best bet. After you show them what you got in the one year, they may be the ones begging you to stay.
Cheers!

Brazilians would kill for a teaching position in a university. You have exactly zero chance to get a position from inside Brazil (like actually any kind of job, without speaking about visa issue that you cannot have if you don't have a job). So best chance is that your university and/or country programs allowing foreigners to teach/lecture here. Exchange science/programs, etc...