They can only be trade at ETH in uniswap as I know. So if you want to keep the fee down you use metamask with a friend. You send your grunt to same metamask and make one big swap. That is the only way I can find out - but I am not an cryptoexpert.

One other way is to use grunt to buy pigs and try to sell them at discord. That is obviously not so easy but I have sold some.