Since felt erasers were used to remove chalk from the chalk boards that would have been the move to use but maybe a stiff make up/ paint brush would work.
You can try 5 water to 2parts vinegar then let it air dry
Sorry, I don't have a suggestion for this case. But I always use "stone" tailor's chalk for everything. You can just wipe it off. Any remnants will be gone in wash or dry cleaning. I hope someone has a better idea for your current situation though.
I am looking at the Intellistitch stitch regulator which can be added. Check their website!
Before my mom purchased her first quilting machine, she actually drove out from Ohio to Iowa to see one for herself & meet Jeff Jochims & has had one every since and said that she'd never buy anything other than an apqs machine.