The wiki page link represents the current state of driving directions in
pgRouting. As I mentioned the process is straight forward, but the
details are very dependent on a users specific data. I implemented it a
long time ago for a client's specific data schema, OSM and Google only
have to deal with they one data schema, pgRouting allow every user to
have different data schema so it is not likely a "generic" solution will
be easy to find.
So that leaves you with with a couple of options:
1. building a solution specific to your data schema along the lines outlines
2. having someone else build it for you
3. using and existing solution like OSM and loading your data into that
4. not having a solution
Contact me off list if you want to consider some contract help. If you
want to do it yourself, I'm happy to help if you get stuck but read
through wiki link again because that is the model you need to follow.