I've been on CJ for a few months now but I just can't work out how to do deep links to a specific product unless a link has already been set up within their CJ product list. With other sites, you just enter in the product page url and it makes up the link containing your affiliate info for you. I can't seem to get the CJ site to do this.
Not all advertisers allow deep linking. If they do you can do it with the instructions on this page: http://www.michellecrofts.com/blog/how-to-use-deeplinking-in-commission-junction/ If they do they will show a "Destination URL" field on the linking code creation pages.