I used to use QWERTY for 20 yrs. I was a touch typist, I don't know how fast, maybe 80-100 WPM. I use Windows 7. I started learning Colemak about a week ago. I tried Dvorak for one day, but it just frustrated me. I did the lessons at: https://www.learncolemak.com/
I did one lesson a day, and repeated past lessons:
Day One: #1
Day Two: #1-2
Day Three: #1-3... and so forth, except that when I got to lesson 7, I went ahead and did the rest. Probably should have stuck with the plan, but I got impatient.
I did make some minor changes: switching the positions of the S and R keys, and the U and L keys because I kept getting them mixed up.
Also, I type a lot of French and Spanish accented characters, but I didn't need a lot of the fancy ones, so I erased them in my layout. And I made a separate "Colemak International" with the dead keys: ~, `, ', ", ^ like I was used to.
I'm real slow now (15-20 wpm?) . N is my hardest key. But now that I am only typing this way, I will get faster soon; I'll post a typing test result when I improve.