I use a Filofax for scheduling appointments, which often change several times a day. Worst case scenario is that more than half my little ‘blocks of time’ are crossed out out and little arrows all over the page point to new times. If it gets really bad I have to remove a page and rewrite it so that I can see where I am supposed to be and when.
I have mostly always used ballpoint pen – mainly because fountain pen takes too long to dry and pencil tends to smudge if the paper it is written on is used extensively. To make things worse, I am a leftie so my hand rubs over things as I write them – smudging both damp ink and pencil.
For the past few months I have been using Frixion erasable rollerball pens and highlighters. They write just like a rollerball but you can erase them like a pencil. They are named Frixion because the heat from friction makes the ink invisible. So the built-in eraser can, through heat, erase without dust.
I really can recommend them. They come in many colors so you can match them to your Filofax! The highlighters are also brilliant.
Just a word of warning -heat does make the ink disappear so if you leave your notes in the sun they will become invisible. Just pop them into the freezer and they will come back.