I am not sure what else you could use
Besides feather-sticks and moss, you could also try:
Scraping wood with the knife spine, like scraping a ferro rod. This will create nice dust.
Sawdust. Easy to make with a sak/multitool saw.
Fluff, from dry tree bark, scraped with spine of blade/saw.
Fluff that grows naturally, like cattail heads.
Fungus, those lumps that grow mainly on tree trunks/roots.
Cow dung, or of any herbivore. Essentially compressed, dry grass.