Trimble's special interest was training guide dogs for the blind. He became president of the dog education foundation that supplied dogs for the Hazel Hurst Foundation of Monrovia, California, and spoke to clubs and community service organizations about the work of the foundation and the need for service dogs. The Hazel Hurst Foundation educated and found employment for the blind, including injured war veterans, and trained German Shepherds as assistance dogs that were given free to each student. By August 1944 the school had supplied the Lockheed-Vega Aircraft Corporation with 300 workers, greatly needed for production work during World War II.