I think raw done properly is great - e.g. a pre-prepared commercial diet like Nature's Menu. Some vets are down on it because people try to wing it and make it up, which leads to all sorts of disasters. Hmm, food down all the time? I'm probably not the best person to advise, I haven't had a kitten for a long time, but I learnt most of what I know from an absolutley brilliant old-school vet we had all the time I was growing up (long passed now), not great with people, but a certified genius with animals and diagnostics. According to him dry food is not the best thing for cats period. Its for the owners' benefit. Don't get me wrong, it won't harm them - but it will cause them to eat less wet, and if their thirst drive isn't strong enough they end up with urinary tract disorders (more dangerous in males as the urinary tract is very thin, but still painful and nasty for femailes). Granted, some cats will drink enough. It depends on the cat. So...I'm not sure. Maybe ask someone who's raised a kitten recently?
Okay toothbrushing. Well first you need a pet-specific toothpaste because obviously they don't spit it out. I use Beaphar but there are loads available online. And a tiny cat toothbrush. Put the toothpaste aside for now. For the first few days you are just going to introduce the kitten to the brush. Show them the brush. Let them touch the brush. Tap and stroke the brush gently on their face. You can do this over a few days. Gradually inch the brush closer to their mouth. They like to have their cheeks stroked, so do this with the dry brush, slowly slowly getting closer to their mouth. Then after a few days try touching it to the outside of their teeth. Don't be tempted to rush. Just a little more at a time.
Then introduce the toothpaste. Not on the brush at first, just put a tiny bit on your finger, like half a pea size. Let them taste and smell it. Its safe for them to swallow a bit if they want. Gradually work up to putting the toothpaste close to their mouth. Then on the mouth. Keep working with the toothbrush 'play' at a sepearate time of day.
Finally put the toothpaste on the brush. The first day, just try to apply to to the front outside teeth, then leave it. When your cat accepts this, start working your way to the back outside teeth with a tiny bit of pressure. Then work on getting them to open their mouth, which they will probably do instinctively. Just a little bit every day, until you can do as many teeth as possible.
I did this over several weeks and the upshot is that one cat accepts a complete brush happily. She seems to like the taste of the toothpaste. This is my rescue so her teeth still aren't great but they're a lot better than they would have been. My other cat doesn't enjoy the brush and will seek to avoid if she thinks I'm going to do it, but if I approach her whilst relaxed and do it quickly she does accept it without a fuss. I put one hand gently on the back of her head while I do it. She is 11 and her teeth are perfect. Btw you don't need to brush for long 15-30 seconds is ample.