Modification Testors contour putty

Has anyone tried using testors contour putty to fill in pits or things like that in modifications that won't seem to smooth out with sanding? I'm almost done working on modifications for a head and I'm pretty pleased with them, but there are some areas where the sanding won't completely smooth out, and I'm not sure how to fill them. Michael's has testors contour putty, which sounds like it could work, but I don't know if it's safe to use on my doll.

 

I have the tamiya putty, but there's no instructions on how to use it, and from videos I was watching, it has to be thinned with lacquer thinner to get a smooth consistency for filling smaller gaps, and I don't know how safe the lacquer thinner is for dolls or the milliput. I bought an acrylic modeling paste today to try though, since it's meant to be mixed with acrylic paints and I know those are safe for dolls. I also saw a couple reviews saying people used it to fill gaps in model kits, so I'll see how it goes i guess!