If the participation process is more than simple information-giving or consultation, there may well come a time when outside resources will be needed. Do a Budget. Produce a Timeline. Designing simulations obliges you to think through who the different interests are, the problems they may face, the rules by they may operate and so on. At their simplest simulations may involve taking a particular issue and getting people to adopt different roles and negotiate with each other.
More complex simulations can run over several days.
I have listed two books in Useful Publications, one educational, and one about management games, but haven't found any references which are particularly relevant to participation process. The technique Planning for Real has achieved popularity not least, I suspect, because it is one of the few packages available. See also Community planning weekends. It is easier to seek forgiveness than to ask permission. How you make things happen within a participation process depends on the style you adopt , the role you play, and what you are trying to achieve.