Tipping in Brazil kind of comes with a ready-made solution for the tourist. In restaurants, and unless specified otherwise, the bill/cheque will come with an additional service charge of 10%. Theoretically, that service charge is optional, but in practice it is routinely paid. No need to leave an additional tip unless you feel your dining experience was outstanding.
In por quilo restaurants, where you help yourself to the food, and in fast-food restaurants, you are not expected to tip. The same goes for taxis.
Some pousadas (small hotels) add a 10% service charge to the cost of accommodation. When you are quoted a price, ask whether a taxa de serviço já está inclusa? (is the service tax included?).
In other services unlikely to be used by a tourist a 10% tip is customary (hairdresser’s, for instance).