I would also suggest doing it geographically by making a map of locations so that you can get an idea of coverage and reuse it again later. Additionally for knowledge putting the flyers in shops like the bespoke ones on cows lane and george's street was quite effective as people picked them up during the Saturday markets.
Other places worth considering are:
The co-op near St Patrick's
Le Cool
The free Metro newspapers carried mentions of Knowledge before as did the Herald.
Seomra Spraoi
The hidden bookshop near Grafton street has a set of poster boxes and if you ask the old guy in the shop he would probably let you put up a full poster for a week as he did this for us before - specifically because we asked.