I think they just need to be harder on it, so many times it happens and there is no yellow produced, because it's early in the game, early in the half, w/e. Yellow card every time, start rolling out double yellows and teams will stop, there was a classic game a year or so ago where City had about 3 or 4 fouls to break West Ham counters early in a game and got zero yellows for it. I think at half time the reading was 9 fouls to one and City got zero yellows for it, then first foul in the second half was a Hammers foul and the ref produced a yellow, this is just generally poor refereeing.
Or alternatively I feel the ref should be able to pull the captain over if he lets one slide and say to him tell the team 'no more, or I am showing a card, doesn't matter if it is a different player you have been warned.'