Best way to learn aside from total immersion would probably be a systems based approach, where you start by acquainting yourself with the phonology of the language, as well as its written form, and once you can reliably identify its writing and reasonably approximate the sounds, then start compiling a phrasebook, with the goal of growing your vocabulary bit by bit as you go, with basically zero pressure. The grammar rules of the language should be the last thing a learner focuses on, because it's the part you need other people to help practice. That being said, full immersion is still the best method there is. But barring that, I'd recommend letters, phonology, vocabulary. Not an expert or a language teacher, just the way that makes sense in my head. [@Xandrya]

One neat thing about the languages you mentioned in that Portuguese and Russian share phonological characteristics, so they sound almost like the same language at times to a non-speaker.