I explained the changeover with a letter and had little problem. First time round we just did the tops, then after a while top and bottoms. There were rounds that we still tradded but when we split the round I managed to loose most of them.
Just type something up to tell them what you are doing and why, ask them to be patient as you are still learning how it works and take your time.
Communication is the oil in the machine, if you don't have it you will get problems.