I just recently remember sites like MMOGA who are key sellers, so instead of looking for a way to build a store to sell keys, you should ask and look for key selling stores. The list of key stores i found for developers are:
MMOGA
There might be more but these are the ones i found. These are the best i can find for advoiding Brazil fees while still selling it online.
I prefer to not use these sites. There are a lot of persons still re-selling Steam Keys of my games there (without my consent of course).
I personally don't care when they have purchased it from a past bundle and decide to pass it over, but I will have a lot of "self competition" in these places.
I still prefer to use my own site and also there's the local currency and payment methods issue.
