You can use soybean any time without worry, though your lawn would rather rest a bit in the middle of summer. I'm holding off on such apps for now due to a fungus concern as well. Actually that didn't answer your question. Soybean will green up your lawn but it won't create a growth spurt. It's more gradual.

With brown patch, the simplest answer is, "Don't do that right now." :-) Stick to the normal feeding regimen and drop soy no earlier than the first of August. We don't want to make the disease angry.