David,
I woudn't use Cetol. It is an excellent product that I have used on boats that stay out in the sun continually. But for a kayak that will be inside most of the time I would use varnish. Cetol will keep a boat that is outside all the time "clean" for about a year. The finish of Cetol is not glossy, although you can apply a gloss coat.
My varnish of choice for new varnishers is Interlux "Schooner 96" and for those who want a more difficult varnish (thicker, needing appropriate thinning) that proviodes the utmost in gloss and UV protection I have switched to Epiphanes.
Alex