Congratulations for making a great choice, I hope you are reading the book though...
In answer to your question, some people do it but I don't believe there's a real need for that. If you start out with good CG compatible CO and gel, any 'cones you may have on your hair will break down and wash off your hair eventually. What you CAN'T do is use your old products with 'cones after stopping the shampoo because then those 'cones will start to build up on your hair.
But, if it makes you feel better you can clarify "naturally" by soaking your hair for a few minutes in a mixture of 1 C. warm water w/1 Tbsp. baking soda, rinse it off with plenty of water, then apply a 'cone-free CO, "wash" with it, rinse, reapply and leave it on, then apply gel.
2A/3A, medium length, layered, colored dark/medium ash blonde - "CGer" since April '02.
"Converting the 'curlskeptics' one curly head at a time..." HWHC