i just put flowers over it and don't bother watering them, and grass still grows back pretty fast. i don't walk on the grass i'm tryingcto regrow unless i have to, since i noticed that it takes longer for grass to regrow if you walk on it regularly.
i currently have flowers like almost EVERYWHERE in my town to regrow grass.... lol... i used to run a lot when i made my town and i didn't realise how ugly it got until like a month later smh