None of those breeds are auto-sexing. Auto-sexing means you would be able to tell at hatch males from females from down color or pattern.
I've not had Anaconas, so I can't say as to what their particular development speed will be. It sounds like others have indicated they develop early so the males telecast early by larger, red combs. (Some breeds are clear that way). You can often tell by 3 to 5 weeks of age.
Barnevelder can be trickier, but generally if you see a black chest coming in it will be male; brown with gold flecks will be female. However until the adult feathers come in some of the juveniles can be misleading with darker colored girls and lighter boys. Eventually the chest color is a good indicator as the adult female will be brown with gold lacing all over her body while the male will be base brown body with black chest and hackles and tail with brown-red bars on the wing tips. Comb size and color will also indicate male vs. female.
Barred Rocks can be trickier too. In well controlled lines, you can tell almost at hatch from the size and shape of the head dot and whether or not there is a black wash down the legs (small dot/black wash female, diffuse dot, no wash male); however, those distinctions vary between lines and definitely do not hold true with hatchery quality BR's. You should have a pretty good inclination by 6 weeks of age by comb size and color (boys much larger red while girls small), also the girls tend to be darker with stripes further apart while the males look lighter with closer bars since the males usually are double barred (should be but hatchery stock can vary). But if you have one bird, it is awfully hard to tell if that is black on white or white on black.
You say Araucana and that you are in Australia....so do you mean the European standard with tail and muff? And do you know for a fact that you have Araucanas rather than Easter Eggers? EE's are hybrids of Ameraucana or Araucana with any other bird on the other parent side. EE's are fun, colorful birds that lay colorful eggs ranging from blue, green, pinkish, brown and even white. Araucanas should only lay blue eggs. EE's can often be sexed earlier as there are some typical color patterns for female and male. True Araucanas need to develop more in order to know. The pea comb can be harder to pick out between male and female as it is generally a smaller comb altogether; however, again the males will have redder larger combs fairly early. Often males will have 3 large rows of peas while the girls have one main row down the middle and two very small border rows.
All said, by watching comb size and color, with your breeds you should have a good inclination by 6 weeks, fairly certain by 10 weeks of age, which can make it hard if you want to add chicks. That is why many over purchase so they can get the number of hens they want. Factory sexed chicks have about 90% accuracy, and in America that holds fairly true. If I purchase 10 birds, I will get 1 rooster. Sometimes you have lousy luck and get all roosters (such as my 2 Barnevelders were both roosters).
If you really need hens, you can purchase the Commercial hybrids such as a Red Star or Gold Star or Black Star. I'm not sure what they will call them in Australia, but they will be sex-linked hybrids. That means that you can tell by the down color which is female and which is male. They are excellent layers and no risk of males. I've filled in my orders with a couple of sex-link hybrids so I know I will have at least a couple of girls for certain.
Post photos at 4 to 6 weeks of age so that those experienced can voice what they think.
Edited by Lady of McCamley - 12/18/15 at 10:15pm