Without being fully immersed in a Cantonese environment (which, depending on your definition, basically only includes Hong Kong and some parts of the Guangzhou

Without being fully immersed in a Cantonese environment (which, depending on your definition, basically only includes Hong Kong and some parts of the Guangzhou area), it's almost impossible to really "learn" Cantonese outside such environments, since there's actually very few resources for intermediate/advanced learners of Cantonese... There isn't a proper Cantonese dictionary (yet). The existing ones either assume you are already familiar with Mandarin Chinese, or are just simple translations to English. There (almost) aren't any children's books in Cantonese. There is very few literature, and serious books written in Cantonese. The reason being Cantonese being traditionally considered a 'slangy spoken dialect of Chinese' not fit for writing serious work. We're trying to fix that, but it will take some time.