Timm began to work as a mechanic, servicing aircraft for Al Wilson, an exhibition pilot, in exchange for flying lessons.

[3] In 1920, Timm's piloting skills were noted for flying an outdated biplane with a Curtiss OX-5 engine from Los Angeles to Bishop California over the mountains and desert.

[7] In the 1920s, Timm began to fly as one of the pilots that performed "stunts" in Hollywood productions, joining Paul Mantz and Frank Clarke as highly sought-out talent.

[10] Wally and his brother Otto constructed a replica of a 1900 vintage Gustave Whitehead aircraft for the 1938 movie Men with Wings'.

One of their modified Beechcraft Bonanza's, the "Waikiki Beach", was piloted on a world record flight by Bill Odom and is displayed in the Smithsonian National Air and Space Museum.