Mix the two batters ( of rice, and urad dal & methi) by hand for best results. Use a large vessel to ferment the batter as the volume will increase in the fermenting process. Do not use a container with an air tight lid while fermenting the batter. Keep sprinkling water in between making dosas to prevent the tawa from getting over heated. Adding a bit of sooji (semolina) to the batter makes the dosa more crisp.