Sales guys tend to think of themselves as lone wolves - out in the cruel world, living by their wits, selling their hearts out. Creating sales teams is an effective way to get cross-fertilization on a sales call. Two heads can be better than one - and it will definitely shake up the same old routine. You will need to address “team” compensation. I once worked for a company that split bonuses into three factors: 1/3 of the bonus was based on how well the company did, 1/3 was based on how well my group did and the final 1/3 was based on my individual performance. This encouraged me to do things that were good for the company and my group. It certainly fostered teamwork and suppressed some of the lone wolf tendencies that consultants have.
Put your existing customers into three categories and develop simple sales strategies for getting more business.