I'd tend to go for some diluted all-purpose cleaner for this:
Ideally, apply with a soft brush, work into the fibers of the top using small circular motions, followed by either rinsing with water, or patting or wiping the dissolved residue until dry using a lint-free (e.g., microfiber) cloth.
Although there are many options for all-purpose cleaners, attached picture shows the one that I'm currently using, and liked enough for my personal needs to buy a gallon of the concentrate! It's a bit spendy in small-bottle version, but reasonably economical in gallon concentrate form. Has all kinds of uses. It gets spots out of my carpet at home (e.g., wine spills) like nothing else I've ever tried.
PS - did you notice there is a new detailing subforum on 986boards here?
Boxster & Cayman Detailing Discussion - 986 Forum - for Porsche Boxster Owners and Others
(This thread would have been perfect as the first new thread started there!)