Boy, it's questions like this that really bring home the fact that Miguel (nckvilledudes) is not still with us - he would have had an answer for you in a heartbeat. The best I can offer is a link to Brian Collingwood's website. Brian has extensive experience in growing clems from seed and has documented his efforts in detail.

FWIW, SAC (C. terniflora) apparently has an ability to seed itself quite easily....to the point where it is considered invasive in certain parts of the country, so it shouldn't be too difficult to germinate by intent :-)

Here is a link that might be useful: Collingwood clematis seed growing site

Terniflora seeds germinate easily. Sprinkle them on top of your soil, covering them only very lightly with soil. I've had good luck giving them 6 weeks of warm, then 6 weeks in the fridge, then back to warm.

They will germinate without the cold period but it is easier this way.

If you are in a zone warmer than z5 they can be annoyingly fertile! In fact they are prohibited in some warmer states. Gooduck!