Not sure, since I've not used Mylar, but couldn't you use any applique font? I would think so, cause you could use a "twinkle" cloth, (sparkle chiffon)as an applique. I do know whatever you do, you can't wash mylar. Someone here did that, and it ruined her design.
I've washed it. Did ok. BUT it was not the mylar the balloons are made of. Could the one that was ruined maybe that? I didn't put it in the dryer, however. I sure hope it washed as I just put some on a jeans jacket!
The designs that I've used it stitches on top of the mylar. It is for a halloween trick or treat bag, so it wouldn't have to be washed. I did hand wash the first design that I did with mylar and threw it in the dryer and it didn't hurt it at all.It was something like giftwarp tissue.I love doing those designs! Thanks