When I was a kid (I have grandkids now), my mom let me make my first string quilt using old newspapers as the foundation. Ink didn't rub off as easily then or it seems like it didn't anyway. Would hate to do it now.
I've used copy paper, notebook paper, whatever is handy. Next time I'm doing something different. I have a stack of muslin squares cut out and I am using those as the foundation and won't have to pull it off. Since there is an extra layer of fabric, I'll use a really thin batting. Will make a nice quilt for those cool nights.