A prototype does not have to be hi-fidelity. In fact a more polished prototype intimidates conversation. Using cheap materials lowers the barrier to participation and is more likely to get a spirited collaboration started. Changes can be made and tested easily. For example I once needed a way to prove that vegetables can be grown cheaply and efficiently in urban areas. All I had to do was to put together a DIY Sub-Irrigated Planter using two 5-gallon food-grade plastic buckets. I scored the buckets from a local restaurant with the rest of the materials totaling $10 and I had a fully functional urban tomato factory. Having the tomatoes growing on my balcony convinced more people of the viability of urban food production than any amount of verbal reasoning would have done.