Hi Julia,
If I'm having trouble separating the seed from the calyx, I leave them in a paper bag and let them dry longer. The calyx will eventually get bone dry and will break apart easier.
If you need them sooner for a trade, let the trader know they are not separated because it is tedious and time consuming. They should be happy to get the seeds regardless!
Remy

Thanks Remy. I'm probably being too impatient anyway, I will try and let them dry out longer. I would like to save some of them for winter sowing this year and I'm just OCD enough to want perfectly clean seeds!