Matt, you can buy curved sureform files that will get you close before sanding (ie eliminate the major step-offs). They are cheap (under $7 US) and save some of the sanding time. I've only done strip canoes and would wonder if the result after sureform filing might be sufficient to go ahead and glass the inside of your kayak?? Clearly isnt smooth enough for the highly visible interior of a canoe, but in a kayak interior we're mainly talking function.