Mixed Media - What Goes with Soft Pastels?

Cold wax medium over soft pastel, it moves it a bit but it's quite nice. 

The wax gives it a lovely softness. I’ve got some wax but have only used it once, keep meaning to.

It was NOT easy - in the end, I used gouache rather than acrylic or oil: the pastel just drank it and burped, demanding more - gouache does sink anyway, use it dry and you have to keep returning to freshen it, but the pastel underneath didn't even mix with it, just slurped it in, in gulps.  Didn't help that I only had Zinc White, a Titanium might have worked better; or even a bit of acrylic with the gouache, but after a struggle I frankly didn't feel like continuing any further.   Nor do I want to repeat the process with different paint, because yes, the problem lies with the surface stability.  All I've done is ruin what might have been a reasonable pastel - but as it was only done on an offcut from my sketchbook, it doesn't matter. So my conclusion is that acrylic will work over hard pastel; and that any water-based paint isn't really going to work over soft/chalk pastel.  Oil, I suspect, would either obliterate the pastel, or mix with it in a grainy sludge.  As Bobby seems to have decided to work this all out for herself, I don't feel inclined to actually try oil over pastel  - especially after this:..................