Having had a talk with Phil some several years ago, I modified his method a bit. I tend to use Humbrol matt enamel for my models, and so have a quantity of mucky turps when I get to the end of a session. I use this as very thin paint, sloshing it generously about, and watching where it runs. It tends to collect in places where corrosion/muck will naturally collect. The only bit to be careful of is the runs down any vertical surfaces, as the surface tension of the turps will make a tear-drop shape. To sort this I have a dry brush handy to give these tear-drops a swift upward stroke, re-shaping the run and getting rid of the surplus. This treatment needs repeating several times, as the effect can be very subtle when the turps dries out. This means that you probably wont over-do it at any one visit.
That, and sailing regularly in salty water.