Since this wasn’t quite the most obvious, and I’ve noticed in two companies so far that “yer doin’ it wrong,” I thought I’d share the easiest and most readable method for stepping through child table rows in velocity, when you don’t want to create a separate template:
#foreach( $row in $sys.item.getNodes( '[i]child_table_name[/i]' ) )
$row.getProperty( 'rx:[i]field_name[/i]' ).String
#end