When the citta slowly, step by step, goes into calm, the citta's habit of going out to the senses and their objects will slowly lessen until one will be aware as soon as it occurs. When one gets to this stage the word "Buddho", mentally recited, will disappear on it's own because the recitation word is a gross object and when the citta goes beyond this gross object stage it will abandon it. When the preparatory word has disappeared one need not recall it. Just keep the citta at the base constantly and notice the feelings and tendencies of the citta in that base.
Luang Pu Atulo