The Sunshine Boys - 1975
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With Walter Matthau and George Burns - They were both a delight.  My job was to age Walter.  Aging his face with "stipple" was easy but he had thick black hair, with a low hairline.  Bleaching is tricky, wigs have other problems so I proposed thinning out his hair down to the roots and using my hair whitener.  Walter agreed.  The hairs that have been cut grow out like the beard and have to be electric-shaved daily.