I'm told, and quite willing to believe, that your salary has more to do with the five minutes of salary negotiation than the next several years of work. I am also told that salary negotiation is very much a skill.

As such, it seems it would be worth a fairly substantial amount of time and money to practice and/or get coaching in this skill. Is this done? That is, how likely am I to be able to find someone, preferably someone who has worked on the business end of salary negotiation at somewhere like Google, who I can pay to practice salary negotiation with?

ETA: I've read extensively about how to negotiate (though of course there's always something more). What I'm interested in is practice.