Get a pair of scissors (I prefer a small set used for personal hygeine that fold in on themselves so you can work with more accuracy) and essentially cut it up into little bits, but for the record, seriously consider investing in a grinder if joints are your main method, they save you massive amounts of time and it requires little effort, they only cost $10-$20.

P.S Coffee grinders work well I hear, thats assuming you dont end up smoking coffee grounds.