I've had good luck with a paste of Dawn dish washing soap, oxy & shout. I used a toothbrush to get under the stitches, as the blue chalk I used actually stained the thread. It did take 5 washings in cold, air drying between, before getting it completely clean. I will never use chalk again. I now use golden threads paper, which I stitch thru with thread less needle and the iron off pounce. Works great! Keep on working on that quilt, I hope it comes out!