With all due respect for the varnish and epoxy afficionados, I have not had good results long term that way. If the cracks are very deep, or the wood is cracked all the way through, the epoxy is going to debond sooner or later due to differential expansion and contraction.
My recommendation is first decide if you really want a gloss finish. If you just want to preserve the wood and can settle for a wood-look and no gloss, Semco has a new teak color that looks quite good and this is an excellent preservative. I had it on all the rails and window trim on my Taiwanese trawler for 19 years without having to remove it. Simply washed lightly and recoated a couple of times a year. No sanding, no prep. EASY! But it doesn't shine. It did get lots of compliments.
If you want gloss, consider Cetol. Again the newer colors look much better than the orange of years ago. It is tough, almost feels soft, but wears well. It will move nicely with moisture and temperature change. Sand or scrape to bare wood, clean and coat the cracks with multiple coats until a level surface is reached (caution, allow two days dry time between coats!) and then apply as much as you have patience for and you get to the color you want. Finish with gloss and keep applying gloss. My 48MY rails were done with Cetol in 2002-2003 and have been regularly sanded and recoated with gloss since, but not wooded down, and they look great. I'm in Florida for the winters and B'more for the summers so lots of UV exposure.
My $.02
Bob
