So your Mod Podge isn't sticky later?!?
Sounds like I didn't do it right. I probably DIDN'T let it dry completely between layers. (My project wasn't a sewing machine case; I was re-covering shoeboxes that I use for storage. They stayed sticky forever so I eventually tossed them.)
I don't think I saw pictures of your case before. If you have them handy and wouldn't mind reposting, I'd love to see it!