@jimbob79 I looked up your town in Australia and learned you're in a pretty temperate zone. I also did a search on the internet using "Australian native plants for screening" and some good links to articles popped up. I'm new here, so I can't put links in my posts yet. But, if you use that search term, you should find the same articles.
A couple that looked promising to me were "Hot Flush" Lilly Pilly (Acmena smithii), and also a few different bottle brush varieties (Callistemon), like "All Aglow" or "Tangerine Dream." Those would be the size you wanted. I got that info from a website called "Gardening with Angus."
I tend to go for big planters when I plant in containers. For instance, I just bought a dwarf crape myrtle tree and I'm going to put it into a pot about 23" wide and 23" tall. It will grow to about 8 or 9 feet tall, so it will be roughly the same size you're talking about. I've been assured by more than one nursery that this size container should be fine for this tree. So, I'd guess this size would also work for your shrub.
Then, what I'd do, is put them in a row with a drip irrigation system. They're pretty cheap to set up. You basically just run tubing across all of the pots - one long tube. And, you either punch a hole in it at each pot, or you install a little spigot into the tube over each pot. Then, you turn the water on low, and they just drip, drip, drip - not using a lot of water, and keeping the plant moist.
The last time I used this type of setup was in a vegetable garden where I used gravity feed. I put a water container on top of something, then filled it with water, and let gravity water the plants through the little irrigation drip tube. Worked great.
You didn't say how long of a hedge you needed to create, but another watering option, which is the one I'm going to use for my tree - is an olla (pronounced oya). It's a terra cotta container that is shaped like a balloon with a skinny neck at the top. You bury it into the pot with your plant with the neck sticking out of the soil. Then, you fill it up with water, and the water will seep slowly into the soil. Same basic idea as the drip system, but more labor intensive, as you have to water each one separately.
For what it's worth. Good luck!
