I completely forgot about this bounty service.
Now I have checked them again and still can't withdraw any of my stuffed tokens there. They asking to import my wallet ie keystore file there.
First of all, not ALL the tokens require the claiming process. Most of rewards for our latest campaign are to be sent automatically, as a usual airdrop.
Second: there is an option to create a wallet within the system or to sign transactions with Metamask plugin.