Practice is the key!

Some things take time. You can't make a baby in a month by getting 9
women pregnant (Warren Buffet). 

After taking a class even from the most talented and popular educator it is obvious that you can't do the same quality nails yet. You already know the technology, what tools you need.
To get the results you need to practice regularly and as often as
possible. 

After 3 days without practicing after new class you will not
remember the biggest part of the technology, brush angle, etc. 

Can you imagine what will happen after one week? 

If you just learned a new skill, practice everyday.

 It is the only way to achieve your goal.