I'm not sure if you are a sports fan....But here is how I perceive and compare consultants....
Some of the best football coaches (college and pro), baseball managers (college and pro), and especially basketball coaches are excellent when it comes to teaching the skills needed to become superior professional athletes (who make millions of dollars each year), they just aren't the athletes themselves. Some were former athletes, just not very good ones. Their knowledge and ability to teach does not directly relate with their inability to perform.
Take Phil Jackson, coach of the Chicago Bulls and LA Lakers. The guy was a benchwarmer for the most part when he played for the Knicks in the 70's. Now he is one of the winningest coaches in NBA history. Although I guess if I had Michael Jordan and Scottie Pippen or Shaquille O'Neal and Kobe Bryant, I could win some championships too (ha ha). Maybe the short, cigar-smoking, bald guy (Red Auerbach) from the Celtics is a better example.
I know what you mean about the stock broker example. Teaching and investing are two different things. You could not begin to sit and count the satisfied, grateful number of people Vanderkooi has assisted over the years. You should look into what they have to offer. It certainly wouldn't hurt.