I started early, it's best to do it that way so they get used to it. I'm not too surprised that your daughter bit when you put your finger in her mouth, since it's not something she's used to. They make toddler brushes with very soft bristles. You can use just water, or a toddler paste that is safe to swallow. With my daughter, I let her play with the toothbrush, but then she never wanted to actually brush her teeth, just suck on the toothbrush, which was a struggle. With my son, I didn't really let him have it until he understood what it was for, and now he easily lets me brush his teeth, and makes (mostly) the right motions on his own. He even tries to spit when we brush, even though he has nothing to spit out, lol. I'd definitely go out and get a brush now, it's a good habit to instill early. If you have another baby, you may want to start early, when the teeth first start coming in, so your child gets used to it. Good luck!