How did Chandbhai create fire in the forest to prepare the chillum for Maharaj?

Your question reverses the roles of the individuals in the event. According to the Introduction (Chapter 0), it was Maharaj who offered the chillum to Chandbhai, not the other way around. The text specifies that there was no fire in the forest where they met. To solve this, Maharaj himself struck his tongs on the ground, miraculously producing a fire to complete the task of preparing the smoke. This occurred during their initial meeting after Maharaj had helped Chandbhai locate his lost horse, which was found grazing behind a hedge exactly where Maharaj pointed.