Build methods with async

I know I can use async or bluebird but really do not know how

I have the follow

function Builder()
{
}

Builder.prototype.heavyProcess ...
Builder.prototype.ioProcessAfterHeavyProcess ...
Builder.prototype.afterHeavyProcessTwo ...
Builder.prototype.afterIoProcess ...

for the Builder.heavyProcess i do in sync way (I think so) for the ioProcessAfterHeavyProcess i'm using async.waterfall

function ioProcessAfterHeavyProcess(cb) {
 async.waterfall([
        function(callback) {            
            heavyProcess(...);
            callback(...);
        },
        function(callback) {
            callback(...);   
        }
    ], cb);
}

but i dont know how to do with afterIoProcess