A quick tip – i have found it very effective to use those cheap and abundant woven fabric shopping bags for saving seeds.
In these photos I was just processing some Italian Kale seed clusters. The seeding clusters grow quite high on this kale and sit off the top of the plant and are hard to handle and dry off in any other way without losing a lot of seed.
Usually I just leave them on the plant till the first seed pods start to brown off a little and look ripe and make sure they have some viable seed in them. Then I just cut the whole fruiting spike off the top of the plant and stick it top down into a large woven bag like this one and then hang it up in a dry space in a shed or garage space for a few weeks.
The seed heads dry out nicely in these bags and as long as there is some ok air movement they just desiccate perfectly.
You then just take them down and thrash the seed pods and old growth about inside the bag and all the seed drops to the bottom. I usually get some gloves on and just rub the dry matter till it is totally crushed and then just throw it out as I work down to the seed at the bottom.
You can then tip the remains into a large bowl of some sort and thresh it about a bit and eventually you end up with a fairly high seed content which can be labelled and bagged for next year or planted out directly in seedling trays.
Given that these bags are very cheap and plentiful and easy to handle and hang up, you can store many seed heads for a long time ready for processing till you want to. I find at the end of autumn I will have up to about 20+ of these bags hanging about drying often I just leave them hanging till spring and plant them out directly.
They are remarkably effective at drying if hung in a good spot.
I use them for the Kales, rocket, spinach, chard, carrots, parsley. mizuna, mibuna, radishes etc and also for drying out broad beans and others beans, peas and other such seeding plants.
They are also excellent for processing onions and garlic etc which need a good drying space. I just find laying the alliums all out on drying mesh etc in our unpredictable weather too space and time consuming.