Mr super clear gloss

Msc gloss is safe to use on bjds and can look appealing in some situations, at least I think so. I used it on a very shiny dark resin color girl many years ago and it made her colors look crisp and her head cohesive to her body where I feel like a matte spray definitely would have ruined it.
It has a slick surface so it's different to work on so it may or may not work for you, but if you have it already there is no harm in trying.
Good luck!

 

I had a doll who was sealed with gloss (actually, I think it was a semi gloss), but it looked like she was sweaty all the time, so I had to have her redone

Teddy

 

If you want you should also be able to use matte as a final coat and it will reduce the shine on the finished Faceup.

 

I enjoy painting 1:6 action figure head sculpts. Most people use a layer of gloss to seal the work, and a layer or two of matte fixative to make everything look more realistic -- like real human flesh. I recently tried that on my newest BJD, that's not realistic at all, and has zero sculpted skin texture, but I liked the result quite a bit and probably would have liked it a bit shinier. The layer of gloss topped by matte fixative make it seem like there's some additional level of texture on there, even if your head sculpt doesn't have any sculpted on it. Which I really like, but might not be for everyone. The gloss will definitely not harm the doll, and it's just as removable as the matte type of fixatives, just a matter of preference. (: