Have just over an acre of grass so didn't want to take whole thing. Any suggestions on getting rid of thatch and what is everyone's opinion on when you should cut the yard super short to get rid of all the dead grass.

I have San Augustine and I currently cut it at 4 to 4.5 inches during summer.

St Augustine doesn't have thatch, it has runners. Cut it 2.5" but not all at once since it's so high now.

https://neilsperry.com/2020/05/choose-the-best-mowing-height-2/

SA still gets thatch

I have followed Randy Lemmon program step by step for two years and I feel my lawn was the best in neighborhood during the drought. However I feel fairly confident I have a layer of dead grass underneath that is affecting growth. I have had to cut my grass sometimes 3 times as week during these rains so it doesn't get to long.

I aerated it today so curious if that helps.

I use a heavy duty field rake on my lawn. It's really good at getting all the dead grass up. I do small areas every week before I cut.

https://www.homedepot.com/p/Razor-Back-24-in-Aluminum-Landscape-Rake-63136/205352521?source=shoppingads&locale=en-US&&mtc=SHOPPING-BF-CDP-GGL-D28I-028_011_TOOLS-NA-NA-NA-SMART-NA-NA-NA-NA-NBR-NA-NA-NA-NonTopSell&cm_mmc=SHOPPING-BF-CDP-GGL-D28I-028_011_TOOLS-NA-NA-NA-SMART-NA-NA-NA-NA-NBR-NA-NA-NA-NonTopSell-71700000098930567-58700007968691435-92700072531088871&gclid=Cj0KCQjwguGYBhDRARIsAHgRm48eixE3RwLbh7ZthaPyqvAdz8txpVhx3ulM0NRsOmMyZhO99m7HqsIaAoYiEALw_wcB&gclsrc=aw.ds