Hi,
The first step is to create a custom post attribute. You can do this on a specific post by putting it in the Custom Fields.
Name must be appId, and the value is your App ID, eg: 476468390.
After that, the shortcodes for that post no longer require the id= attribute, and can be used simply as follows: [asl_icon]. You can still use other shortcode parameters as usual.
Using this feature also automatically adds an App Smart Banner to your page for the appropriate app.
Note: As of WordPress 3.1, the Custom Fields box is hidden by default, but is accessible by the Screen Options tab at the top of the page.