Hi,
We are in the same boat. We are applying for a 189 Visa on which our youngest daughter can come with us as she is 17 and still in education. Our eldest daughter is 22 and in full time employment. She will have to come on a WHV and do 3 months rural work, she will then be legible to apply for a second year. Hopefully within these 2 years she will find a willing employer to sponsor her. There are a couple of other options, but to be honest that's too far down the line to even contemplate as things change all the time.
We spoke to several agents before appointing one who we felt we could work best with, but they all gave the same info for the eldest daughter.
Get a good agent, I think they are worth their weight in gold.