That's why I pointed you to the PanelManager source which very likely
implements all the methods that you may need.

You just need a custom CollectionEditor, which you associate to the property
via the EditorAttribute. You will need to add a reference to
System.Design.dll in order to use the CollectionEditor.

Imports System.ComponentModel
Imports System.Drawing.Design
Imports System.ComponentModel.Design

Public Class MyControl
...
<Editor(GetType(ButtonCollectionEditor), GetType(UITypeEditor))> _
Public ReadOnly Property Buttons() As ControlCollection
   Get
       Return MyBase.Controls
   End Get
End Property

Private Class ButtonCollectionEditor
   Inherits CollectionEditor

   Public Sub New(ByVal type As Type)
       MyBase.New(type)
   End Sub

   Protected Overrides Function CreateCollectionItemType() As System.Type
       Return GetType(Button)
   End Function

End Class
...
End Class