May I know when can I start brush my kid's teeth ? And what should I use to brush his teeth?

I started when mine was 4 months old, he didn't have any teeth then, so he used those without bristles, every bath time he will hold the toothbrush and 'brush'. it's been a habit and routine and till now at 28 months old he will ask for his tooth brush,and toothpaste and brush on his own.