The two vowel lengths sound too different to me (native speaker) for this to really work. The difference is the difference between aː vs a in IPA. I'm struggling to find a similar vowel length example in English and Wikipedia only has examples with an Australian accent. :)
Yeah, it doesn't really exist in English. I'd even argue that the Australian pronunciation doesn't change the vowel length as much as it adds a chain shift [1] (similar to the Canadian/Algonquin "ou" pronunciation).
It's one of the most difficult things to pick up when learning Japanese as well. There are lots of words that are basically homophones except for vowel length and tone. To an English speaker they tend to sound identical, but to a Japanese speaker if you get it wrong the result is unintelligible. For example "地図" (in romaji: chizu and pronounce cheezu with a short "ee") is "map" and "チーズ" (in romaji: chiizu and pronounced cheezu with a long "ee") is "cheese" (though they have the same tones... I'm struggling to think of an example with different tones as well as vowel length).
The thing that helped me the most for this was singing songs. Once you understand that there is a necessary rhythm to the words, it makes it much easier to use that rhythm in speaking. Or at least it did for me -- YMMV.
Even if it's not really a vowel length change in Australian English, I'm pretty confident it is in South African English (as spoken by me and many others). Ferry/fairy are distinguished by vowel length only.
