That's not the problem; I already have air drying clay and even the "white" variant is actually a light grey, but what I want to do is produce faces that look very much like their counterparts from the filmed and CGI seasons (especially when I have no suitable source face). I used to use paper cut outs by themselves, which obviously doesn't sit well with the plastic faces on unchanged models. When I made new customs after the collection reunion, I decided to try and trace with hot melt glue to make the faces stand out. It worked alright for four characters but became frustrating when I tried my first one for an engine, so it might just be the methods I'm using.
Either way, I've started trying to build the first version of my improvised Henry, which is also proving quite difficult and not very robust at the moment. It might be better to bring the Spencer chassis inside and test fit while building instead of strictly relying on Gordon. He will naturally have the same design flaw as the 2012 version where the firebox is too wide and blocks out the cab, though I hope to get around it in some way.
