But that's not necessarily what was used here--I seem to remember a lettercolumn of the time, in Green Lantern if I remember correctly, in which Julie Schwartz says that the effects on the original page were produced any way the artist could manage--pencil, crayon, what have you. The breakthrough was in Jack Adler's technique of making it reproducible by the printing process being used.

Russ Heath also did a great run of GI Combat covers in wash.
Life'll kill ya
--Warren Zevon