Have you looked at Tarmak? With that you can type whatever you like, mostly. It changes 3–5 keys at a time, and people have done the whole progression from 9 days to months, depending on many factors.

The main idea of Tarmak is to not hurt your productivity much, letting you go on with your daily life and typing while you transition to full Colemak. Also, the first steps are the most beneficient so you start to get a better typing experience quickly. Check out my sig topics.

I used keybr (Still learning colemak)

I have been using it for 18 days now, 8 hours of colemak according to the stats. I rarely use it for work yet.

It took about two weeks to get all the keys. I started with like 8 or something, typing about 25 wpm. Since then my average speed has increased to 40, but realistically it's higher now. (My average is 50 today, for example, full keyboard)