Add nofollow attributes in links should work just fine … just tested it. I vaguely remember having this discussion about it working/not working; can’t remember why or why not and if it didn’t work, what I did to fix it…
Any way, you can even use this plugin to make it easier to add the nofollow attribute.
I also tested using this plugin, so manually adding it and using this plugin both work for me.
Hope that helps!