How early should your child brush?

Recently I was talking to my friend about our kids and the topic somehow arrive at brushing of their milk teeth. So far I've only wiped Jonas's teeth and gums with a clean damp cloth but haven't started on "real" brushing(with toothbrush) yet. She told me I should start soon as she read an article that says the milk that the kids drink will harm their milk teeth if not cleaned properly and can definitely cause cavities. I decided to find out more by doing a Google search on how old toddlers should start brushing. 
Most of the sites advised to start even before the first tooth appear preferably around 4months old. Babies are actually born with their teeth formed but are just hidden beneath their delicate gums. Parents or caregivers should use a clean damp cloth or a soft silicone finger toothbrush to gently rub the gums in order to prevent bacteria from forming on the surface. When the first tooth appear, continue cleaning with the finger toothbrush or you can switch to a normal toothbrush. The ideal toothbrush head should be small for easy maneuvering in LO's small mouth and the bristles should be soft. This should start at about 6months of age and done at least twice a day to get kids used to the idea of brushing their teeth. Usually most kids will be taking solids at this age thus brushing is important to prevent the sugars from harming their milk teeth. A tinge(about size of a rice grain) of fluoride toothpaste can be used but do not try rinsing their mouth with water as they may swallow the toothpaste. Instead, teach them to spit out the excess toothpaste and leave abit of it on their teeth for the fluoride to work better. It was highlighted that the ingestion of fluoride can cause diarrhea. By the time they reach 2years old, the amount of fluoride can be increased to about a pea size. Brush their teeth and gums gently in a circular motion as they are still very delicate. If a child struggles, you can try letting him hold his own toothbrush. With some practice, kids will learn that they need to brush their teeth. Try to let them watch you brushing so that they can learn too. Adult supervision and assistance will be needed until they can do it by themselves. I also read about flossing in between their teeth on one of the sites but I wonder if it could be possibly done since getting them to start brushing is already such a challenge. On another website, it states that a child should be brought to the dentist before he turns one which I felt was too early. However, it is a good idea to start bringing them for half yearly dental visits at a younger age before going to primary school in order to ease their fears about visiting the dentist.
Armed with this newly gained knowledge, I bought a Kodomo brand toothbrush suitable for 0.5-2year old and a tube of fruity gel Kodomo toothpaste for Jonas. I've been trying to make him brush his teeth without much success for the past few days. After I start to brush his teeth, he'll start to suck at the toothpaste shortly and prefers to bite the bristles and the toothbrush head. Then he wants to hold the toothbrush. When I try too hard, he'll turn his head away or shake his head indicating that he don't want to brush. I guess he's still too young to understand what we are doing. But I'll persevere with it and not give up. Hopefully he'll like to brush his teeth soon as I noticed he already have half of his milk teeth grown(about 10). He is currently 18months old and I'm abit regretful I didn't start him on it earlier. So with this bit of information shared, I hope you will have a better experience then me when taking care of your kid's oral hygiene.