If you have a file /dev/.devfsd then you have devfs
you should read this before doing anything
this can cause sever problems if you do it wrong.
As far as startup scripts, I usually make a file called rc.devfs or something like that, and make it executable. Then run it from rc.local.
The most common links are created already, there may be a need to use mknod to create some dev files in some cases. All the needed files and links can be created by the same script.
creating your own file is much easier than modifying your devfsd.conf file and may prevent problems later with updates to devfsd.
if you do wish to use devfsd.conf to make changes or additions you should save a copy of the original.