My mom always put straight lemon juice on stains on white and then let them lay on the grass in the sun. It seemed to work pretty well.
Also, there is a teacher, Cindy Needham that teaches classes on quilting on old linens, tablecloths, etc. I know she is teaching at Road to California in Jan. in Ontario, CA. She also teaches at Empty Spools Seminars at Asilomar this year. I am taking her class there in April. She teaches other places also. I understand she is a great teacher. She has a website and you might put her name in a web search to find out more. She might have ideas for appliqueing something over a stain while quilting.