I used to built airplane models when i was younger,since my father used to own a model shop. The best thing you can do to make it shine is apply 2 simple weathering techniques,once the model is fully built and painted. I don't know if you are familiar with them,but they are useful to anyone interested so i'll try to describe them.
First one is dry-brushing. Use this to create the effect of accumulated smoke on the tip of gun barrels by using a small,round brush for accuracy. Also good for exhausts using a bigger flat brush,as well as aluminum colour to simulate stripped paint from overuse of painted metallic surfaces( like the rims and deck on the bridge,or any metal handling levers/wheels on guns for example,you need to use the gun metal colour for that). Use a colour that resembles a smoke hue (or unpainted metal as stated above),this might by anything from black to brown or a mix of them,depending on the colour you're painting over. For example,a brownish black would do well for smoke trails on a gray undersurface like a U-boat. What you do is dip the brush in the paint,then brush across a paper napkin until the marks start resembling smoke trails. At this point you brush across the model surface you are interested in until there's no paint left on the brush,or the desired effect is reached. Repeat as necessary,but don't overdo it,you have to be subtle
The second technique is known as wash. This involves use of solvent,so you need some knowledge of different colour pigments. Generally,model paints are divided into acrylic and enamel. A good solvent for acrylics is water (or window cleaning fluids for cleaning brushes) ,while enamels can be used with their own special solvent available in each model shop (or white spirit for cleaning brushes). Generally, the solvents used for brush cleaning are too harsh for disolving paints before use,so don't use white spirit or window cleaner for this technique. Especially white spirit might in some cases harm the plastic itself and ruin your model.
One last thing,acrylics dry much faster than enamels. You can touch an acrylic painted surface about 20 mins after the last brush,enamels need 1-2 hours. Of course it's not advised,as even then the paint is not fully dry and you might leave fingerprints. Enamels may take up to 5-8 hours to fully dry,while an hour or two should suffice for acrylics.
What you need to do with wash is add a relatively high amount of solvent to the paint before use (don't do it in the paint's can,use a small cup instead or you'll ruin the rest of the paint). Then you generously apply on all surfaces that have engraved details on them (like the deck grills or the sides of the hull),let the dissolved paint run among the lines for a few seconds and then wipe it clean with a soft paper napkin. This has the effect that the paint only stays inside the engraved lines where your napkin can't reach,essentially toning them and making them more visible,sort of like painting a shade. It's also good for simulating oil and rust leaks like those seen in the pictures of the assembled model. Adding solvent in the paint is the whole trick,as it makes the paint more or less transparent. Again,don't overdo it.
The tricky part is the solvent thing. If you paint the model with enamels and wash with enamels on top of it,when you wipe with the napkin the solvent will clean the underpaint as well. What you need to do is paint with acrylics and wash with enamels or vice versa. Again,the preferred colour mix for the wash depends on the colour of the surface you're washing over,like in dry-brushing. Look in the model photos posted in the link for reference and try as you go mixing.
The best thing you can do for washing? Paint with enamels (generally a lot more accurate colours to choose from in the enamel range),and then add an acrylic varnish coating. The coating must be thin,in order not to "seal" the engraved details(thin means solvent again,i think varnish works best with a special solvent,ask the guy in the model shop).Varnish coatings are also available in model shops,but you need to spray them,they don't work well at all with a brush. If you don't have an airbrush you have to choose an aerosol can.
After the varnish is dry,you can wash over it with enamels,since the acrylic coating will protect the main enamel colour from the enamel solvent in the wash. Use a gloss varnish coating,as it makes the surface smooth and let's the washing paint flow more smoothly. Since military vessels and aircraft rarely use gloss colours though,you need to make it mat again. Simple,when the wash is dry,spray one more thin coating of acrylic varnish,this time not gloss but mat.
With these two simple technics you can simulate a lot of effects of wear and tear the atlantic and the crew are performing on the boat. Generally,dry-brushing is used on the edges of surfaces,where people walk and touch things and wherever friction is present,for smoke trails and to add lighter tones as highlights on parts of a surface "sticking out" (by sticking out i mean the opposite of reccessed,the exact word escapes me at this time :rotfl: ).
Wash is good for adding shadows on reccessed parts of a surface and simulating leaks,as well as giving an all-around "been in use" image to your vessel.
Hope it helps,enjoy the building process