Instead of trying to block posts you could turn things around by creating a channel or multiple channels that allows content that you want to see. Go to Settings/Channel and then 'Add new entry to the channel list'. Now you can create a new channel that e.g include tags, excludes tags, from another channel or a certain circle and so on. This is pretty neat to fine tune your stream. As an example I created a Dutch channel (see image). It's not bullet proof but together with blocking certain persons or organizations it gets me pretty far.
However I'm not sure if TweeseCake does support this.