In mail art we used to do 'assembling zines' where X contributors would send X number of prints/multiples/photocopy/rubberstamped pages, then the organiser would collate fone page from each person into a zine and send 1 copy to everyone. I think this could work well with download codes. Everyone has surplus of these things due to bandcamp's annoying 100 codes minimum.
everyone could send one page of codes, and the zine organiser could cut them up and staple into tiny booklets (or paste into a larger zine) and send one to each artist.
downside: NOBODY EVER REDEEMS DOWNLOAD CODES UNDER ANY CIRCUMSTANCES. Could include some kind of curse against anyone who doesn't create a bandcamp fan account and actually download the albums
might actually do this some time but please someone else feel free

especially since international postage costs are too high so best within one country
