Saving Sub-Documents With Mongoose

I'm pretty new to mongoDB and the popular ORM Mongoose. And I just spent way too much time trying to figure out the proper way to save sub-documents in mongoose. The mongoose documentation shows you how to assign values to each property of a sub-document when pushing it onto the sub-document array, but how often will you do that? If you are using Mongoose, you probably have a model for the sub-document and you are probably passing that around between your controllers and models. So how does one persist a model of a sub-document to the parent document? Here is an example:

First, the model and schema stuff:

var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;

var childSchema = new Schema({
     foo: String
});

var Child = mongoose.model('Child',childSchema);

model['Child'] = Child;

var parentSchema = new Schema({
    parent_foo: String
    ,children: [model["Child"].schema]
});

var Parent = mongoose.model('Parent',parentSchema);

model['Parent'] = Parent;

And here is an example of how to save the sub-document (assuming myParent is an object of type Parent and myChild is an object of type Child):

myParent.children.push(myChild);

References:
http://mongoosejs.com/docs/subdocs.html
https://groups.google.com/forum/?fromgroups=#!topic/mongoose-orm/IIaVEHcEDTw