I don't know the answer to your problem with Dullcote, but it seems like
there was a lot of discussion in the model railroad press about using alcohol on
Dullcote and obtaining results similar to yours. I don't know how you could
search for this in the Model Railroad Magazine Index, but IIRC, the
discussion took place during the first six months or so of 1991. I'll try to find
some reference to it in my old magazines.