Podge no offense but it sounds like you are breaking the kiss rule! (keep it simple). Why can you not milk the fresh cow in whatever order she comes in, and dump the milk into a bucket from the jar, very quick wash out if the jar by shoving the hose in each cluster and suck up abit of water is all that is needed afterwards. In any case trying to separate cows in the holding yard is definitely not safe and sustainable, is there any easy way to draft them as they leave? All that is needed is a simple drafting gate, and pin or race that stretches to the back of the parlour where they can go back in to be milked lasted. The likes of that which if you don't have now shouldn't cost more than a grand or so would be a hell of alot more useful and important to do rather than sinking massive money into a new parlour if your existing parlour is suitable otherwise.