I've developed a bare bones random chart, though of course customized to our campaign and my character. It would make sense that the elf in our party, for example, if he had more elven followers than human.
The tricky part is determining the skill or profession of commoners or experts. My inclination was to take the suggested Craft skills from the text and roll that, then to determine from that if a Profession would match up. Problem is there are 21 "most common" Craft skills mentioned and 30 Profession skills. So, you can combine Craft Armor and/or Weapons for 20, so you could roll a d20. But attempting to equate a skill to profession requires more work than the 30 or 40 minutes I dedicated to this idea. Though, with 20 crafts and 30 professions you could use percentile and each skill has a 2 percent chance on the chart.
So, for an expert, I figured you could first roll d4 and figure out if they were an expert in Craft, Knowledge, Perform or Profession and determine the sub-specialty from there.