For decals you don't technically
need MSC but it's always better to have a coat under and over whatever custom work you're doing on a doll. It's a good rule of thumb since MSC is a sealant, but it's invisible. Some people use liquid sealant just over the eyes, but I don't know how that would work with a decal. Probably fine.
Also...ack, it sucks when they don't give you 'spares'!!! <_< More profit for them I guess? XD;;