I really wouldn't recommend blowing into the camera body because your breath will be full of condensation. If you are going to do it yourself, definitely get one of those pump/blower things, hold the camera upside down, aim the nozzle into the camera body but don't start poking it around in there, and squeeze the squeegy bit. If you are lucky the movement of air around the body will dislodge the particle without you having to muck around with mirrors or do anything more intrusive.