Definitely I would not use any automated tool.
Reasons:
You don't control the destination category,
Different articles directories use different engines, which means you never know if backlinks are inserted properly,
You won't have any access to submitted articles (login and pasword) in the future.
Do it manually, it's worth it. Am doing it manually and the result is significant!
Just a comparison to automated link directories submission:
It is the same thing in the basis and it doesn't work at all.