the essential i remember would be oil painting on hardboard. it was easy to get, as commonly used in furniture making, and one side would be usually smooth and glossy. i can't tell what exact paints he was using though. i'd rather should say the best on the market, though i know it is not an answer. i now listened to two interviews about his technique and paintings, and there was no specific paint mentioned. he was telling that being indecisive during the process makes the pictures surreal, and painting in darker light makes the paintings brighter, but technically imperfect. i think he was teasing and trying to demythologize the artistry. while i listen to him and his disliking, i realize how the son was similar in thinking, even though seemed more moody. as for your question, i'd rather ask someone who would remember the paint tubes, have pictures of the painting studio, or you can seek it in the videos backgrounds, the tvp movie is high quality