I think if you analize the top coaches in each league it would seem to suggest being a top player is the easiest/quickest route. For those whom are without that pedigree the youth system at a smaller league club would be the more likely starting point.
These are obviously subject to being offered the position but if you have some football specific qualifications one would hope they would assist one in being offered a coaching position at a Club.
i have an even better prospect take an african team an get to the second round of the world cup and people would be running allover themselves for your signature...ask Bonfere Jo and the white witch doctor Philip toursier