Norton's are some pretty hard stones and it sounds like you got one shaped like a banana. If it's still a ways out, you may consider a more rough approach like some wet/dry sandpaper in a more coarse grit & then follow up with your DMT. Naniwa SS's on the other hand are one of the softer stones and if it's taking a long time you aren't getting enough water on the DMT to rinse out the "mud" so the diamond stone can cut.

This is a good task for you, it will teach you patience...which is most definitely required when honing razors. Take your time and sometimes you may have to walk away & come back when your head is right...just don't give up!