I would recommend you a very simple way to get the answer to your question. Put this on Google search. You will get a large number of protocols. Now you select which one is suitable for you.
A 3-fold increase compared to that of previously highest rate made by Monteiro et al. (2005) for Bacillus subtilis spore production
Monteiro, S. M., Clemente, J. J., Henriques, A. O., Gomes, R. J., Carrondo, M. J., & Cunha, A. E. (2005). A Procedure for High‐Yield Spore Production by Bacillus s ubtilis. Biotechnology progress, 21(4), 1026-1031.