The only place you need abrasion resistance in the cockpit is where your heels rest. Put down an extra layer of glass or dynel about 4"x8" and you've done it. Coating the whole entire floor of the cockpit with a black coating is kind of missing the point of what you're trying to address.

For low maintanance I put down fill coats of white tinted epoxy, sanded and two coats of paint. A bright interior is more user friendly than a black one. On the bottom of the hull I did the same but with an extra later of glass. One kayak had a narrow strip of heavily coated graphite/epoxy down the centerline from 3/4" wide to 2 1/2" wide under the cockpit for dragging over straight edge surfaces.

I don't see why you'd need a super slipper interior.

Regarding graphite for the exterior the only rational is dragging a kayak over rough surfaces where the wear ISN"T on the last 8" of the keeline. The only time I see that as likely is a loaded kayak where you aren't in it and you're dragging it through the water over rocks and you're in the water. When you're IN the kayak there's so much weight that durability is a function of skin strength so the wood doesn't get dinged. In that case a few thick mills of graphite epoxy is irrelevant, you might as well have few extra thick mils of fine glass and epoxy on top of the regular hull glass. for 275lbs of kayak, paddler and gear coming to rest on a rough beach it'll be the thickness of the glass and epoxy over the wood that'll matter for durability,not the slippery thick coating of graphite epoxy.

Sure a graphite bottom is slippery and doesn't show scratches like a varnished hull but if durabilty from scraping IMPACTS is a concern I'd add more glass before I added graphite.