There is definitely no highway that accesses Aguas Calientes from Cusco, so taking a bus for the entire journey isn't a possibility. The trains are your best guess! The best way to get to Machu Picchu would be to take the coach to Aguas Calientes. The 3.5-hour prepare journey is https://machu-picchu-tours50370.blogocial.com/little-known-facts-about-machu-picchu-tours-62675497