So you want to get out a settler in one turn to keep that growth thingy going? Whip a unit that you want and gives you surepluss hammers. Build science so it keeps the surepluss for a turn. Then whip again and keep the surepluss. If they get to angry /low city pop chill for a while and build science, then whip unit out and keep storing that surepluss This way you can pop out units in high food whipping towns and then pop out a settler in a turn or a worker in a turn keeping your growth going. Also you can use this teqnique to save up forest chops for wonders or units etc. Its especially usefull for saving up forrest chops for wonders where you havent connected a resource yet giving you bonus.