I've done this quite a few times. I'm of the opinion it is a very different challenge than from doing it as Prussia because you have a lot more to balance diplomatically, domestically, and militarily. Your tech choices have far greater consequences and every loss of manpower on the battlefield could be the end of your nation. Austria is ripe for breaking apart the portion you want and absorbing it quickly due to internal strife that must be overcome if you are playing as it. It is the Victoria 2 version of giving a cat a bath. It is not simply a weaker version of Prussia with the same goals and ease of method to achieve them.
Prussia is a cohesive industrial powerhouse you usually have to spend decades occupying, carving up, and running their industry into the ground while fending off the other GPs from your hard won prize. Playing as it is almost as simple as declaring war and marching. I mean that unless you take a very long time or get into a war with France and Russia there is not much diplomatic contention to deal with. You wait for Victoria to ascend and fight Austria for Hegemony while pumping points defensively into your target lands. You don't really have to worry about who your allies are as long as you can take on all the ground threats sent your way. Nobody should be powerful enough or covetous enough of the German lands that are not yours to take something you'll need later. Russia might take some of Austria, but it won't be German lands you care about. The same with an Italian or Ottoman ally.
As Austria I tend to go after France as quickly as possible after securing Russian guarantees, the mountain forts on the Italian front, and the first war against Prussia to take the largest 2 industrial states and start the truce timer. Defensively break France against the mountains and blockade them in the Mediterranean until you have wiped out much of their military power and given them some sizable war exhaustion. You might even get lucky and have a crushed Prussia ally them and answer their call, breaking the truce with you. Once you've crushed them you should be able to keep them peaceful for quite some time with the threat of Russia's alliance while you are finishing up in Prussia. You'll have to constantly check diplomacy to fight for position in your sphere. You will also have to constantly shift your NF around to create soldiers, officers, and administrators because you certainly cannot afford what you need with the sliders and your losses will outstrip the natural promotion rate due to battle anyway. Cozying up to Spain and Ottomans when they become Secondary Powers is not a bad idea as long as you are willing to help them remain strong. You can use their armies and navies against Prussia without fear of losing territory. Ottomans might cause you to lose Russian ally temporarily.