Which is the best gunite machine (shotcrete) for a swimming pool company?

Question:less wastage , maintenance free

Answers:
Since the conditions you have to work with are unique to your area, there is no one best for all. Some are better in cold weather climates, some for clay soil, etc.
Your best bet would be to call the companies in your area and ask them what type of machine they use, and how do they like it.