If you want anything from the guildbank, this is how you get it.
first link the enchant or whatever it is you want, then link the item you want it on.
also write what mats you have fixed by yourself.
you can trade your grinded items for stuff in the guildbank.
If you feel like donating stuff to Juancarlos, he will feel like giving you stuff back.
Juancarlos is cheap, so if you sell something to him, he will probably not pay you the full AH price, but on the bright side, you are helping the guild.