I can only report on limited use of Dacron. I have also used foam effectively. Others can report with more experience. Haven't heard anyone recently using Kapok.

I use it in a 400 3 inch and find it does the job well.

The RCBS Chargemaster electronic scale/dispenser makes it a breeze to weigh correctly. The scale/dispenser were around $300 but were definately a good pick up.