Before you begin painting the bathroom, unhook the shower curtain from the hooks holding it onto the rod.
Remove the shower curtain from the bathroom. You can take this opportunity to wash it in the washing machine, or just set it in a dry sink until you are ready to reinstall it.
Wait 24 hours for the paint to completely dry after you apply the final coat. Hang the shower curtain back up on the hooks over the rod. The curtain will not take dry paint off the walls.