okay after looking at the pics... wow
i would get a plastic spreader and mix some of the west system 406 filler, the silica stuff here
to a peanut butter thickness and spread a layer in to the cracks. this will fill them with something that has some strength, but is hard to sand, make sure you dont leave any real high spots. then sand any high spots, then mix some more to the thickness of mayo, and roll it on with a fine foam roller, this will give you some build up. once again hit any real high areas with sand paper, then use west 410 filler this stuff
to a thick paint consistency, and roll it on every where you dont want non skid. the reason for this is you wont need to sand it under non skid, it will hid it. you will need to do a light sanding, but be gentle you will sand thru it fast. then do a second coat with the roller. when it cures start sanding gently, with a sanding block. when you find a low spot mix some more but thicker and use a spreader to fill it. then sand again, when you are happy paint with choice of light colored paint.
this will about a gallon maybe a little more ( more if you need to the sides too )for a 30 foot boat which you did not say how big you boat is. it will probably take 4 days of nice warm weather, if colder use a faster hardener. you would be smart to do one half the boat at a time. let the first half cure while rolling the second half, then sand the first while the second cures. if you time it right you will have about a 4 hour rest, between the first and second coat of the day with the second coat curing over night.
if doing the hull too, you can work non stop by doing sections and while it cures move to the next section. if you are careful with the 406 filler and not leave and real high spots with the hull too i would say 5 days.
when done you will have a nice hard smooth finish that should last 20 years. the nice thing is the 406 will be ding resistant and the 410 only acts to smooth it out, but is softer