There are free tutorials, as well as paid trainings. Remember though, all consultancies will have an add-on with shortcuts allowing you to increase your efficiency significantly.
Above all though - actual ppt proficiency isn't very important in the grand scheme of things; I laugh every time I see a student writing "PowerPoint proficiency". Excel, fine; PowerPoint... nah. What matters is how well you can tell a story, not how fast you figure out how to change the font on a slide.