Oil painting alteration problem

I've been approached for advice by a lady who is attempting to paint a portrait, but decided to alter one of the faces of the several people in it...  <div> </div><div>She mixed the paint with Liquin, quite thickly by the sound of it, and when she came to alter the face, rather than scrape the old paint away and start again she went in with more thick paint, plus Liquin - and finds the paint just won't adhere.  </div><div> </div><div>I've given my own advice, without waiting to come here because it was a bit of an emergency, which is - in very short form - to scrape it all off and start again, getting rid of the first layers of paint and Liquin with a pen-knife or painting knife if she can.  I've also suggested that in future she build up the paint without any added medium, and use Liquin only for glazing, or for making paint workable for finer details (and even then, I should personally be a lot happier with just a mix of Turps and Linseed).  </div><div> </div><div>Any oil painters out there with ideas?  It would be good if Martin Kinnear of the Norfolk Painting School were out there, but I know he's going to be busy as usual.  I can't think really what else to do other than remove the paint, which sounds as if it's thick and clogged, and the Liquin: snag is, Liquin dries to a very strong surface which I know is going to be hard to remove if it's been in place for any length of time.  So suggestions welcome.  </div>