

I’m sorry to have to say, but the idea of “hair training” is a myth.
The oil glands (which are known as sebaceous glands, and produce an oil called “sebum”) are controlled by genetics, hormones, and stress. Sebaceous glands don’t have any sort of “sensor” to tell them when to produce more/less oil, so washing or not washing won’t make a difference.
Hair training is a myth, so take their advice with a grain of salt.