Hi Ian,
I collect kauri cones with a pole pruner and a long pool net. It's a two person job to cut the cones off and catch them in the pool net so that the seeds do not touch the ground and if they explode, you do manage to catch a lot of the scatter. Takes a wee bit of practice to get the technique right. Seeds need to be sown immediately. Their viability drops off very quickly even after a few days. Put them in the fridge if need be. Also make sure the seed is all viable. This is easy to do by touching the seed and if it's good, it should feel hard and not squishy. I find there are few viable seeds in a cone (but that can depend on the age of the tree). Hope that info helps. Good luck.