Some hard seed takes forever to germinate. If you go back to nature you would find that animals would stand on the seed and this we can emulate by scarifying. Some growers use a file and scrape each individual seed, but I find it much quicker to just put them on a concete or paved surface and brush my shoe up and down over them.
Try the "bite test" to speed up the germination of hard seed. If the seed is hard when you pretend to bite on it, soak them in water over night before planting. Some growers use boiling water to soak their seed but I prefer to keep things as close to nature as possibel and I've never experienced boiling hot rain.
When planting fine seed, like Buddleja saligna, add equal parts of sifted soil and mix well before planting as this will eliminate the problem of plantlets being squashed.