I think it will be faster than QWERTY, but I need practice with it to get used to where all the characters are. Does anyone have ideas for sites to practice typing with? I think I just need large amounts of kana text to follow along with, basically.
On Android with Gboard it’s a bit more buried. Look under: settings > system > languages & input > virtual keyboard > Gboard > languages > add keyboard > Japanese 12 keys.
As far as apps that you can use it with… I don’t know any specifically. I tend to favor the Japanese QWERTY keyboard, but when I do use the 12 key, it’s usually just in the browser or in messages. You should be able to use it anywhere that will accept Japanese text.
You could use notes or a concept email or whatever to type anything you want. Also if you know somebody who is also doing japanese, you could text in Japanese to them. Also, Japanese language section here, try to participate on mobile.
Write the word, and the katakana version will be in the list of suggestions somewhere. If the word’s normally written in katakana, it’ll be closer to the top.