Right, the C-spanner have 2 holes on there so you can attach a breaker bar to help getting the rings loose.
Once that is loose, then it should be easier.
If you got down a little bit and then it is stuck, it mean some debris may have got into the thread.
wind them back out and clean it up, and if it is possible, remove it from the car and clean it up.
This is one of those time where you need to be easy on the coilovers and don't force it.
You don't want the debris to cut the thread up...
Inbox clear now so let me know if there are anything I can help.