My kids 3 and 4 wanted to show their artistic prowess on my walls. They drew some pretty pictures of smiley faces and monsters etc. They wrote with ball point pens and in some places they used permanent marker pens, crayons, graphite pencils , nail polish, chalk you name it they used all available resources. I wish they had spent their talent on paper. Here I am looking at those work of art and was supposed to smile at their talent, but ended up having the reverse effect of making a monster shrek face.
I spent considerable amount of time scrubbing with all purpose cleaners like 409 , clorox and others. I scrubbed so much that paint started peeling. I went to Home Depot and Menards first in the cleaning section and could not find anything other than tile cleaners and then in my next visit thought of using paint thinners but nothing worked. Later when I was browsing I came across a product called Motsenbocker's LIFT OFF
That was a savior When I sprayed on the ballpoint ink marks the ink just melted and I could just wipe off with a cloth. This is truly an amazing product.
This can be found in Menards, Homedepot etc.
They have other wonderful products for graffiti removal and others. Good luck on your cleanup and I give it a very high rating. As a parent of little kids.