Once the pods start to split open the natural tendency is for the seed to disperse. Hold the pods over a bit of paper in a dish and tap with a pencil, any ripe and retained seeds will dislodge and you can tell those from the "chaff".
If you lost out this year, a little tip for next year is to use a pin or tiny craft peg to hold a bit of old panty-hose round the pods to catch those seeds before they escape.