Horses, dry jelqing, [words=http://www.mattersofsize.com/forum/penis-enlargement-forum/12539-slow-squash-jelq-nothing-give-me-better-expansion.html]slow squash jelq[/words], iso compression squeezes all work both chambers. If you think about where pressure is applied when doing any kind of manual girth work (constrictors and pumping included) the force is exerted to both chambers. Thumb and forefinger may alter where the pressure is more directed to, but in my experiences the difference is minimal at best. Personally I say stick with squeezes and jelqs and you'll be fine. Majority of your depth comes from the CCs, as the CS only makes up about 1/3 of the total circumference of the penis. Do it all and be consistent and you'll get there.