Thanks for the response.
I ran /etc/rc.conf_mount_rw via SSH - it returned successfully very fast.
I then ran /etc/rc.conf_mount_ro - it took a few seconds, then also completed successfully (both commands verified by looking at the output from "mount")
After the filesystem was mounted read only - I ran fsck -y /cf - and it produced the following result:
** /dev/ufs/cf
** Last Mounted on /cf
** Phase 1 - Check Blocks and Sizes
** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Check Cyl groups
33 files, 8520 used, 92535 free (39 frags, 11562 blocks, 0.0% fragmentation)
***** FILE SYSTEM IS CLEAN *****