After his playing career ended due to a knee injury, Johnston coached in the NBA, in other professional basketball leagues, and at the collegiate level.

[2] He led the Red Devils to an undefeated 16–0 regular season and ranked second in Ohio in 1945–46 as the team won its finale 82–19 behind Johnston's 38 points.

After failing to distinguish himself in minor league baseball, he tried out for the NBA's Philadelphia Warriors at the team camp in Hershey, Pennsylvania in 1951 and was signed to a contract.

He also worked as an assistant coach under Jack McCloskey with the Portland Trail Blazers and at Wake Forest University.

[15] On September 28, 1978, Johnston died of a heart attack at age 49 while playing basketball with his son, Scott, in Bedford, Texas.

[16][9] A memorial service was held at North Lake College and at St. Paul's Methodist Church in Hurst, Texas.

[17] He was survived by his wife, Phyllis (Wilson); three daughters, Nancy, Barbara and Kay; and twin sons Daniel and Scott; and three brothers.