Hello Kurys,
Welcome to the forum, it's good to see so many fellow Canadians joining.
It's that time of the year here, at least in Ontario, where these smelly little creatures seem to spend a lot of time crossing roads at night only to meet their end under a passing vehicle. It makes the drive to work in the morning a fragrant experience.
Just so this is not totally off topic, I also use vinegar as Unit8 mentioned in his post on 7 Sept. 2009. One must use caution when using any acid, I've found that leaving the medal in the vinegar, with extreme cases, works well but timing is everything. I experimented with a "junk" medal (unnamed of course) and it is possible that even an acid as mild as vinegar, which is only 5% acetic acid, will remove detail with too much exposure.
Regards
Brian