How to plan a multi-city tour in Europe using private buses?

I’m organizing a multi-city tour across Europe with a group of friends, and I’m trying to figure out the best way to manage transportation. We’re thinking about using a private bus, but I’m not sure how to plan the route and make sure everything runs smoothly. I want to visit Paris, Brussels, and Amsterdam in one trip. Has anyone done something like this before? How did you organize the bus routes and stops? I’m also curious if it’s possible to have some flexibility with the schedule in case we want to stay longer in one city.