Sorry for the simple question but I get the impression there are different schools of thought for this.
Can I use the same pens on the chart as I would for the whizz wheel? I'm told a non permanent soluble pen works for a whizz wheel which I guess makes sense as you only need to mark for a short period to do the calc and then rub clean. Does this approach work for the charts where the marking needs to be retained for a longer periods?
If I use a permanent marker, what do I use to clean up? Are china graph pens better?
