Yes, but its (very-)sub-optimal, hard, and the results might be less than stellar.
But you might also have not that much choice. There are few Latin speakers in Australia. A few Gàidhlig speakers. Less ancient Greek speakers. Opportunities for communication events are limited. And what if your situation is even less tenable? The last native Manx speaker died in 1974, but there are an estimated 1800 speakers today? Plenty of indigenous languages have <10 speakers, and some are actually dead but well-recorded. I’m not even an educated amateur on language revitalisation, so I’m going to stick to talking about Greek in this post, but I suspect the principles are generalisable.
Comprehensible Input is still king. If you don’t have speakers giving that to you in conversation (and even if you do), you need to get as much rich , appropriate, language content as you can. So, read everything you can, work within your abilities as much as possible and resist the desire to tackle difficult texts unless you have to; rad aloud, to get your mouth moving. And get as much audio as you can – conversation material is best, soliloquies are okay; written literature being read-out is good but arguably not the best thing; oral exercises aren’t the worst thing either. Listen, comprehend, listen again.
Learn the basic of question and answer. This is easier than you think and the pay-off is great. If you can construct questions, you have a means of turning any text into a conversation piece. All you need is to get used to asking questions: start with sentence-type questions, then move on to the interrogatives (In English: who, what, where, when, why, how; Greek: τίς, τί, ποῦ, πότε, τί (διὰ τί, ἵνα τί), πῶς; and others…). Questions can be done in Greek, at the level of story, paragraph, sentence, even clause. This lets you (a) have a conversation with yourself, (b) have simple conversations with others, (c) compose simple sentences and stories that build off texts you’re already working with.
If you’ve come through a traditional grammar-translation curriculum, it’s also not that taxing to learn basic grammatical terminology, especially for Latin or Greek, since they are almost all Latin terms anyway and the Greek forms basically are equivalents. And that permits you to have grammatical conversations about texts too, if that’s what you love.
If you have friends, ahem, students, then start inflicting spoken Greek on them. Start easy, simple, and fun. Prepare well – script up as much as you can before hand so you have phrases to mind/hand. Doing some of the WAYK universal speed curriculum is a good way to do this. When I first did this, I would keep a cheat-sheet handy. It’s no shame to say, “hey, we’re all trying to do this thing, and this little reference sheet is to keep us speaking Nice Pure Attic not some degenerate barbaric language, ahem, Koine.”
Related to the above, develop a habit of note-taking when you are trying to say something and can’t find the right word or structure. And then after a session of whatever, take that list and figure out how to fill in the gaps. I use English > Greek, and Latin > Greek lexica for that, or go away and find the right syntax structure, or ask a friend.
Talk to yourself about whatever you can. If you don’t have other people to talk to, and even if you do, you need to talk to yourself. Why? Because you’re the conversation partner who is always available, and who always understands what your trying to say. Talk about things around you, talk about things you have vocabulary for. Just get talking.
Lastly, look and pursue opportunities to talk with others, or at least listen to others talking. There’s audio resources (not much, let’s be honest), videos on youtube, there is spoken Greek out there to listen to. There’s also a weekly online chat that is freely open: https://latinandgreekchats.weebly.com you don’t even need to speak. I’m never there (alas) as it’s a terrible time for my schedule. And lastly, yes, you can sign up to classes. CKI, which I mentioned in the last post, also I see that BLC is starting to run some classes in Koine not just Hebrew. There’s also some conversational Greek offered through Telepaideia, again terrible for my schedule so I can’t tell you what they’re like from experience.
I don’t have a repository of links for communicative ancient Greek; there’s one here (http://www.latinteachertoolbox.com/ancient-greek.html) but it’s a little out of date. Perhaps its time to make a repository, there’s not lots of material, but there’s stuff out there, and its often a matter of scouring the internet for it….