Creating a class using Bluebird promises

I'm writing some code - a class with numerous methods I would traditionally use callbacks on and wanted to check that I am taking the correct approach.

// Callbacks
function Foo() { };
Foo.prototype.bar = function(cb) { 
  // Some async stuff
  cb(err, res); 
}

// Bluebird
function Foo() { };
Foo.prototype.bar = function() { 
  return new Promise(resolve, reject) {
    // Some async stuff
    resolve(res);
    // etc...
  });
}

Good to go? Or is there a cleaner approach? Most docs/tutorials are about promisfying existing callback based code and I am interested in creating a promise based class from sratch.