Just a thought, but one to keep in mind if you don't want to scrape your soil and haul away when you try to sell your land: Whatever method you use, should be consistant with EPA lead base paint removal procedures. You don't want to blast the toxic gunk all over the place, but may be able to build some visqueen setup to catch the liquid gunk and keep it for approved disposal. For sure, the lead dust that will occur if this stuff dries out, is a serious hazard. Maybe the wet vac could be used to suck the stuff off. I would start with just one fender or something small, set it up with visqueen to trap the stuff and try it out.
Real estate people have been known to ask for disclosure of any known hazards prior to a sale. There have been folks caught up in this who have then been held up with very expensive cleanup costs and potential liability. Hope this helps.
