Well to this day, and i will do into the future, and have always only used a good quality Lens Pen, the Original large ones are the best.
I have been using this method since my first Canon 5D and with all the other Cameras since
Never had a issue, and you would be surprised of how tough the sensor filter really is.
Cleaning is a breeze, don't waste your money and send your camera to the service center it wont come back any cleaner.
Leon