Normally I would have washed it first, but because I was using it as the background for applique, I thought the finishing on the muslin would keep it looking better since I know muslin tends to be wrinkly. I did wet it then used dry iron to dry it after damp. The creases seemed to start to disappear, but came back after letting the yardage sit while I was cutting.
I'm a little leery of putting a 50% vinegar acid solution on the material, but it's not too bad if I can get the squares machine appliqued quickly and the top assembled this weekend so I can quilt it and get it washed before I bring it to my friend....hopefully by next week if I can get my energy level moving
Thanks for the ideas!