I know bathrooms are a bit of taboo subject, but there are definitely some things you will want to know before you go.
As to terminology, bathrooms are known as “Os Banheiros” or “Os Sanitarios”. While the former is more commonly used (and found on signs), with my horrible Portuguese accent, I find people are more likely to understand me if I say the latter. You don’t need to actually ask “where is the bathroom?” (Onde é o banheiro?), like in English, just raise your voice at the end of the word to convey that you are asking a question.
However, you probably won’t want to use the public bathrooms for anything besides urinating. Brazilian plumbing is not the same as Canadian. This means that bathroom tissue does not go in the toilet. There is a small garbage in the toilet, and that is where you are supposed to dispose of the soiled paper. The garbage is changed frequently, but it still smells. Also, it is a somewhat small, so you have to use paper sparingly. Airport bathrooms are the worst though, so I would definitely recommend against those. Go during your layover in the USA (assuming you don’t fly direct), and then you should be good until the hotel.
At people’s homes, or in hotel rooms, you are more likely to find a bidet. If it doesn’t work, check the hose for a handle, not everyone uses the bidet, and some people turn it off without realizing. Bidets, however, are the wave of the future. Read the reviews of bidets on Amazon, and the only complaint you’ll find about them is that people get addicted – once you get used to a mini shower for you tushy, it’s hard to feel clean without it. I don’t understand why these things aren’t common in Canada. There is the occasional time you will find one in a public bathroom, but those are far and few between.
Handheld units are by far the most common, use it like you would use a showerhead. The pressure can be a bit strong before you get used to it, so start slowly. Paper is used to dry, otherwise your bottom will be wet just like when you step out of the shower (which, you butt basically will have).
Otherwise, the washrooms are fairly normal. You may occasionally see an open air urinal behind the back of some bars. Brazil generally has signs that ask you limit your paper towel use to two sheets, to help with the environment. Note, that while hand dryers are usually even more environmental, they largely undermine washing your hands at all, and that doesn’t even consider the issues of pull doors.