I was certainly taught Celsius Fahrenheit conversions in the past but would forget the actual conversion math.
What was needed was a better, simplified method to remember the comparison of the temperature grades by using a simple rule than trying to remember the math. Then learning a few data points on the Celsius scale would make it much simpler.
For me, a good first step would be to remember that every 10 degrees Celsius would be 18 degrees Fahrenheit.
Then I realized that I wanted to concentrate on every 10th degree Celsius: 10, 20, 30 and 40 degrees.
So for: 10 degrees Celsius it would be 50 degrees Fahrenheit.
20 degrees Celsius it would be 68 degrees Fahrenheit.
30 degrees Celsius it would be 86 degrees Fahrenheit.
40 degrees Celsius it would be 104 degrees Fahrenheit.
For me, this is easy to remember quite quick and fast.
Remember the KISS acronym.