For years I have been using paraffin on my pedals and cleats (SPD and Look types) because it works, it sticks, and it does not “attract” dirt. It’s particularly useful in dry gritty situations and in the rain (It doesn’t wash off as easily as liquid lubes.). I do not have any experience with using it in muddy conditions.
The wax can be softened with a hair dryer or a heat gun (just don’t let it get too hot) to allow it to be easily applied. I just rub it on the parts about once a week or so to make exit and entrance easy and to eliminate cleat squeak.
I wonder if it could also be used on a seatpost in a carbon fiber frame?
I don’t see why not. On the other hand, I don’t see why, either, as your approach sounds like a hassle.
I use the Effetto Mariposa CarboGrip, which is easy to spray on, and it stays on and really holds. But certainly you will not damage a carbon post with the paraffin, assuming you don’t crank up that heat gun too high.