Actually I went and tried it already with my Cleo. x) I wanted to start doing the new face up already. And I thought that well, MH's aren't so expensive compared to my other type off dolls. :D
So this is the type of spray sealant I used:
Army Painter anti shine matt varnish
It worked well, and it gave both the head and body really nice and smooth surface. It has been almost 2 hours since I did the base sealant, and I can see no damage on the dollys "skin". :D I hope this helps, if someone else is also wondering what kind of sealant to use for MH dolls.
Still it would be interesting to hear what sealants you pro people use for these, options are always nice. :3 Specially if you can mention names of the brands or something! What was the paint on sealer you used,
DollyKim? Paint on sealant could give a nice touch to finished lips, maybe I could try it too. :3