Some good tutorials have been written by very active forum user Ozz (thanks again):

GSA Captcha Breaker Review - How To… published on 2014-11-04 by Matthew Woodward

GSA Captcha Breaker - How To Get Started published on 2013-03-28 by GSA Software

CB VS CS for Article Captchas published on 2013-02-21 by adelogroup