I think not mowing it too short is the key with the St. Augustine.
....lost big patches to drought last summer... how do you reseed/repair large bare spots?? thanks for your thoughts
ymmv
Since you used the words “patches” and “spots”, I’ll recommend you look into chinch bugs if you haven’t already.
Your repair choices are either sod or plugs.
I’m not an expert at all; this has happened to us before, too. It took awhile for it to cover the area again, but I put more sprigs in the area, and otherwise just gave it more water that the rest of the yard. I think it took so long because it was under a tree and didn’t get much sun. I try to water a couple of times in the winter now so this doesn’t happen again.