2- Use national focus to increase immigration to colonial states, and some technology increases colonial migration (the middle culture one, +10% education, +?% colonial migration). When you have a decent number of your culture in a colony (I find 5-10% is sufficient), switch your National Focus to promote Bureaucrats, I find they tend to come from your accepted culture. I used this strategy during my Boer game and it worked like a charm, took about 6-7 years total per colony to achieve statehood. I'm not sure if there are ways to get a new accepted culture, other than events (I noticed the USA started accepting Afro-American culture during the game, I assume this was caused by an event), but for statehood I think only your primary culture works. I'm sure if you're an Italian or German country that unifies you'll begin accepting the other parts (North German Prussia accepts South German, North Italian Sardinia accepts South Italians, etc.), though I haven't tested that.
I tried the immigration NF but it didn't work, but Iwill keep trying.