Traditionally, microbial cells are plated on a petri dish using a glass rod. Look at this youtube video. This can be very time consuming if you have many plates to spread as they have to be spread sequentially. Alternatively, a number of glass spheres can be added to each plate and the plate can be shaken to spread the liquid evenly. Look at this video for a depiction of the procedure.

We use 4 mm beads, slightly smaller than the ones in the video above, I have found that 5-8 spheres does the job well. The beads can be stored in 70% ethanol, washed and reused.

Worthington, M. T., R. Q. Luo, and J. Pelo. “Copacabana Method for Spreading E. Coli and Yeast Colonies.”