If it is not cutting at all you are going to need more than a chinese natural ( no one knows if its a 12k or not, each stone is different) to bring it back, or you could sit there doing endless laps. Since you seem to be across the pond, look into the naniwa 3k/8k combo stone, should be about 70-75 pounds for you, maybe 80 euro depending where you are. Learn to get a good edge on the 8k side then add the pastes sprays, or a finishing stone later. It will be in your benefit when you need to do more than just refresh a blade later. Try about 10-15 on the 3k, then 20-30 on the 8k, then no more than 10 or 15 laps on the pastes or sprays, then strop and shave.