I'm assuming that Kessler was already an animator in 1931 based on the group photo (link below) where he was placed in forth row from the top and beside animator Nick Tafuri. And in a 1935 Animated News, Kessler is noted a being a member of the Johnson crew alongside animators Tex Hastings and Don Figlozzi.
(courtesy of Ryan Englade)
At some point Kessler may have been shifted into Seymour Kneitel's crew - possibly after Crandall left to head up his own crew. A Fleischer animation crew would average 6 animators - that number included the head animator/de facto director. Crandall's departure would have left a hole in Kneitel's crew - one that Kessler may have filled. My guess is based on similarities between the following gag drawing and frame grab.
Kessler gag drawing from Oct.'36
The above Popeye drawing is arguable in the style of Seymour Kneitel's 1936 cartoons - and leads me to believe Kessler may have been part of Kneitel's crew at the time of the drawing. Below is a frame grab with drawing similar to the one above.
Update: Check out the comments for some links to Kessler's comic book work.