Are some Educators still teaching to use 100-grit nail files on the natural nail plate?

Look at the scratches on the nail plate created by using a 120-grit nail file. In Doug Schoon's "Face to Face Volume 1" book that is available in English, French, Dutch and German, you can see the effects on the nail plate using nail files with 120, 180 and 240 grits.

There is no valid reason to use 100 grit file on a natural nail plate. Nor should any professional ND be using an acid based primer!

20 to 30 years ago this was necessary because gels and acrylics had poor adhesion. Modern products have much higher levels of adhesion - some even don't need a primer to be used. Yet these ancient techniques are still being taught.

This is why it is so important to attend classes and be careful which Educator that you choose. Some are still stuck in the 1990's.