I have enough mmf already made to make tappit letters; and I really don't want to make a new batch but I will if I must. I believe I read mmf doesn't work well with mmf alone. Can I add tylose to this or do I have to add it in the powder sugar stage when making it? Thanks!

You can add the tylose to the already made MMF. I just did so today. I sprinkled a little bit onto the MMF and worked it in and let it rest for a little bit. It makes it stretchy like gum paste and worked really nice. I hope that helps

Yup, I add it to already made MMF all the time when I need to dry something like letters or purse handles or figures. I wouldn't add it at the PS stage because I usually use such a small amount of fondant compared to what a full batch of MMF makes.

Thank you both! Enjoy your weekend.