no better motivation to hone your honing skill than by having only 1 razor that you maintain yourself.
experience is an excellent teacher, but not a very forgiving one.
if you already have a well honed razor, then the 12k should be good. It will take more strokes, so there is more chance of you screwing the edge up. But you probably will not be able to overhone with it. But with the 12k you are screwed if you somehow damage the edge by whacking it on something hard (including that 12k).
Don't be afraid to use your second hand to steady the toe of the razor. My honing improved a lot after I started doing that.