I used to check in the shower every morning - that way it was at the same time each day and in the same position. I checked my CP and my CM at the same time.

When my CP is high - I can't reach it.
In terms of feel my general rule of thumb was it's hard if it feels like the tip of your nose. It's soft if it feels more like your earlobe. Medium was always a bit subjective. I was never any good at open or closed because I have some cervical erosion around the os.

HTH