I read alot and most of the time i find what I find is not always true to form.Hibiscus to winter sow? Not true in my case.I grow alot of things.Start with fresh seeds,soak them in warm water if you want to sometime it helps.I'm a rebel I don't follow that pattern.moist potting soil.Here some that are growing now.Sunset Hibiscus.Propagation by stem cutting,two ways I use.First new growth in catcus mix,cut about a 6 inch piece,put in sit it under a shaded spot,generally within two to three weeks its rooted.Step number two,again new growth cutting,clear jar , take a cutting from a weeping willow , put them both in the jar together.within a couple weeks you will start to see roots.

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Well, it depends also on the hibiscus. There's hardy, tender, tropical, and so on.
I only had experience with the "tropical" ones, and only propagated by cutting.
And...the Hibiscus moscheutos which is a garden hibiscus over here. very hardy. I only propagated this by seeds sown in spring, in pots, and then transplanted when big enough to handle.

I gave up on tropical ones as they were always loved by spidermites and as all my windows are on north, there's not much sun and well, not so many blooms to make me happy.