I wash my fabric just as I do my regular laundry. Because of repeated staining issues (in my regular laundry), I stopped using liquid softener and switched to dryer sheets. I do not use them when prewashing fabrics though. I do use the dryer sheets when washing the finished quilt. I've done this with Quilts for Kids and have not had issues with them but I agree checking with the specific charity would be a good idea.