From what I can see, the ships are airbrushed mostly with lights/minute detail being hand painted. For something this small, good masking (blue tack or poster putty) is the key. For the hand-painting route, you need good paints the level out well (games workshop or vallejo).
Weathering for small stuff isn't all that different from larger vehicles. A nice dark wash is a good start, then you can follow that up with any "isolated" weathering you want.
On the big striped ship, I can see where they airbrushed the torpedo? tubes in the front with a dark brown/smoke color, and their is evident overspray. For something this small, you need either a really good airbrush (with a really small tip) or you need to use pigments or weathering compounds. I use the Tamiya weathering sets for streaks and smoke. They also work well for creating a dry-brushing effect. The raised detail/rivets are also dry-brushed. Other details look painted on.
For battle-damage, you can use a razor blade to gouge out bits of plastic, then weather that. You can also use the same "chipping" techniques used on armor models. At this scale, using the sponge technique for chipping would work find. Just tear off a bit of sponge, dip the edge in paint, blot off the excess and then dab it around hatches, etc.
Finish with pigments. You can use them for rust, stains, streaks, fading, mud, etc. There are tons of articles on pigment use you can check out.
Looking at the water some more, I think they airbrushed various blue tones, then they dry-brushed light grey or white over the crests. Again, at this scale, dry-brushing will help tremendously.
Also, I may not build stuff quite that small, but my Star Wars model page illustrates several of those techniques better than I can explain them. Hopefully all of this gives you a good place to start.
Cheers