As a tool and bronze rusher (I DON'T TURTLE!) this is a tactic I employ with a high amount of frequency. I will outline some of my basic tactics and rationales here and would certainly welcome additional insight.
TOOL RUSH WALLING: Lets face it tool units get blown away (with a few exceptions) by bronze units. If your slinger rushing the worst thing you can see is shang cav @ the 13 minute mark from your rushed ally. On any river maps walling in your enemy is realtively easy (unless they have long shallows) and is almost a must tactic. By walling in your enemy you prevent his villagers from running and opens up the possibility of "resigning" your enemy within the 1st 20 minutes which should win you the game. Of course the converse is also true this prevents enemies from coming to the rushee's aid. On a non-shallows map walling is considerably more difficult but remember that the helper is somewhat limited in their knowledge of their allys map because of a lack of writing. Walling of a few key choke points can buy your tool units a considerable amount of time to bring havoc on the rushed enemy.
One last note: Many individuals who play CA civs never mine gold at all so they can't make cav/camels or units that can break down walls fast at all, thus greatly improving the odds that walling will be even more effective (until they get ST's). This is of course another strong case for combined arms, so mine a little gold next time your egypt...and BUILD A STABLE!