Centrifuge tubes in my experience are excellent for storing pollen. Makes life super easy to just insert a q-tip or arts/crafts brushes work great too. Don’t much care for the small baggy’s they like to get brittle and crack with years of storage. Found out the hard way.
Pro tip: Let your pollen come up to room temp whenever taking out of your freezer and wipe that condensation off. can be a pollen killer and lessen your chances of successful pollination.
Storing in tubes has been very successful. A buddy of mine just used “BamBam” pollen that I collected damn near 2 years ago. Seeds for days… You can see here how I collected if interested…