The enamelled top of my Aga has become dull and dirty over the years and I wish to restore its gleaming, black finish. 'Astonish' paste has been recommended to me but I'm cautious about using any abrasive product which might damage the cooker's gloss surface. Any recommendations of paste/scourer etc which will minimise elbow grease, maximise shine and leave the enamel intact will be gratefully received!