Plain old school chalk works well but, you have to mark as you go or do some remarking.
I will never use the frixon pen again to me it was a waste of money. Yes it will iron out but any change of temp under 42 and the marks come back. I used it to mark a sampler wall hanging for a class. I had ironed it, no marks, put it in a box with my other supplies carried it from the house to the car. When I arrived at the class the marks were back. I tryed Ironing it out then washed it, then took it out to the car in the same manner, marks came back. I went back to my #2 pencile and a good white eraser. They have never failed me.