Patchy Bermuda grass.

What can I do to help my bermuda lawn grow a little thicker? I limed it and fertilized it about a month ago and that helped a lot. There are still some spots where it is thin. These spots have more weeds than the thick areas. Will weeds prevent bermuda from growing or is it more likely something else? It's not shade. I'm trying to avoid weed killer if possible. I was thinking about spreading some black cow manure. Also I heard that aerating the lawn helps, is this true? I'm in north alabama. The soil is mostly clay and acidic.
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