Used it neat, I asked the customer if he had any vinegar as I'd heard it can remove the lead stains, he brought out white wine vinegar which I poured onto a microfibre, and rubbed the stained areas which were runs coming down from some of the lead work. Definitely looked better after I'd done it, customer was pleased as he had mentioned the marks before and I'd explained that they were stains and wouldn't come off with wfp.