I don't know what style cranks you are trying, but, I have slammed them an the biggest Manns 1- in crawdad pattern or Chart./Blue. I actually throw it in between the rocks and the grass in the little channel. Usually, the area in which you are casting is only about a foot wide and you need to put the boat right on the bank, but I have had some incredible days on those cranks on low tide.
If you have spots that are choked with grass on low tide. Try it when you can see a visable channel between the weeds and rocks when the tide starts to come in. Those fish sit back in the grass and face the shore. When the shad run up and down the little channel, they attack. Thats what I did in the Fedeation tournement in May. The weights were down for everyone(like 43 pounds to win for 3 days), but I scrownged up almost 37 pounds on my 1-. Finished 12th out of 120.
Just another Idea for the bag of tricks.
Good Luck
Cam