i put my flies in an appropriate sized plastic container for the particular swap i'm in. i dont use altoid tins, but thats just me (cant stuff 12 bass flies in there)
then i self address one envelope with my return address
at the post office i ask for return postage from the swapmeisters address
insert the swap box and return envelope in a larger addressed envelope and have that weighed. on its merry way it goes
my toe tags are a little different than most. i use business cards for toe tags. i put a foto of the fly and the recipe on it. i then stab the fly to the business card and put that assembly into a 3x4 ziplock bag. 9 times out of 10 thats how i do toe tags.