Compost to help retain moisture and replenish the soil microbes that might have died off with the wet dry cycling.
Mow the grass (preferably St Augustine) as tall as your mower will go. If it goes to 6 inches, mow it at that. It loves to be tall! If you choose to ignore my enlightened suggestion
and go with bermuda, the opposite is true. Mow at one inch and mow frequently. That will give you the strongest stand of bermuda. If you choose to go with buffalo grass, then I consider you to have been buffaloed by the hype for that raggedy grass. You might be able to recover from a buffalo lawn by treating it like St Augustine (weekly watering and mowing with seasonal fertilizing). It will still have more weeds than anyone should have - in my humble opinion. Tall, dense, St Augustine will do wonders to hold water for you. My next door neighbor in San Antonio has not watered her nice stand of St Augustine in 4 years, so I know it can be trained to hold water between rain showers of any natural length. She didn't mow for at least a year and has gotten this huge return for putting up with the scowls of neighbors.
Water deeply and infrequently. You'll have to start this slowly by watering to the point of runoff at first. Then see how long the grass goes before showing signs of stress. If it is a week, then you're in pretty good shape. If it's a few days, then you'll need to work on stretching it out. Wait until it shows the dry stress signs and water the next day. Water a lot. If it only lasted a few days since the last watering, try doubling the amount you water (from one hour to two hours in each spot) and see how long it lasts.
Fertilize with organic fertilizer. I use corn meal from the feed store at 10-20 pounds per 1,000 square feet. Organic protein sources will provide food for the surface microbes which in turn feed lower levels. Those lower levels will darken your soil and increase moisture retention considerably. If you have nothing growing now, you might add some molasses to the mix to get the microbes kick started.
If you start this today, you should see great improvement by September.