How do I populate a ComboBox in an "edit" form?

[butr0s]

I've got a form that I'm using to edit a user profile that uses two ComboBoxes which get values from two different stores. I create the form window and load pre-existing values into it like so:

var win = Ext.create('PPKC.view.profile.Edit').show();
var form = win.down('form');
		
// Load form values from record
form.loadRecord(record);

This loads all my textfields, but the combo boxes are blank. I don't see in the documentation how to load remote data into a combo box before the user clicks on it. Is this possible?