I just spoke with the Michael Harding himself.  First impression: a  most affable and generous gentleman.  Here’s what I asked… and what I’ve learned.  Note: I’m paraphrasing our conversation.  I would hate to try and quote him only to have someone call him and say “but I read some where that you said the following blah, blah, blah.”  He actually says quite a lot on his own website, so go there to get the words direct from the horse’s mouth.

Q: How quick will smudging the Vermilion kill me?
A: As with anything toxic, avoid contact.  The key thing with Vermilion (Mercuric Sulphide) is to avoid ingestion.  Skin MIGHT be enough of a barrier… but I’m thinking of using what I’m inclined to call a “finger condom” to see if the reduction of touch greatly affects my manipulation of edge.

Q: What to do about “beading”?  (This is what happens when you try and apply paint with your medium and it doesn’t stick… but instead looks like beads of water on a duck’s back.)
A:  Try cutting an onion and rubbing it on the surface.  Will do!  This response amused me as I have lately been using a potato.  The potato has seemed to work, but I am as yet undecided on the quality of surface it leaves.  (Note to self: just used it on the early stages of “Delfina.”)  If the onion doesn’t do it, Mr. Harding suggests the application of an egg yolk, only the yellow part; pass from hand to hand in order to remove the white part of the yolk.

Q: Is there a genuine odorless turp that I can use?
A: He mentioned W&N Sansodor, but by no means was it a mark of approval.  He noted that anytime you depart from the real thing, you’ve compromised the substance.  I have Sansodor… but no little about it.  Will research further.

Our discussion ended on color.  For flesh tones he suggested I try the Vermilion with a Yellow Ochre Deep (a semi-transparent color), and any lead white.  He also mentioned his Trans Red Oxide.  Final note on Vermilion: he says despite rumors, he has not had any success in “blackening” the Vermilion, i.e., it is his belief that it is a stable color.