Re: U-Boat colours, "For the most part Type VII U-Boats were grey...All external vertical surfaces down to the normal trim waterline were painted this colour, in reality a medium grey of very neutral tone. The upper surfaces of the saddle tanks and the band on the boat's side between normal trim waterline and the lightest trim waterline were painted dark grey. Deck surfaces were, for the most part, made of wood which was painted a dark grey compound (This would wear over time and exposure to wind, rain, salt water, and sun, both great bleaching agents. Becuase of this, I expect the wood surfaces on a weathered boat were actually
quite light as the paint compound wore thin and "bleached out"). The extreme fore and aft sections of the deck were standard light grey. The underbody was supposed to have been painted with a red antifouling compound (This seems to have been an early practice) but seems just as often to have been covered with the dark grey waterline colour.

The standard wartime scheme of light and dark grey was gradually implemented as boats were repainted and new ones joined the fleet during the winter of 1939 and the spring of 1940. After the beginning of the war, U-Boats rarely sported an evenly applied fresh coat of paint. Unlike the surface fleet, the U-Boat fleet was heavily deployed, with boats spending the minimal time in port necessary for repairs, etc., leaving little time for anything but the most necessary repairs, and the most repainting. This would often lead to "patchy" paint jobs. Unless they were fresh from refit, operational U-Boats were usually streked with rust and soot". (Source is Robert C. Stern's "Type VII U-Boats", published by Brockhampton Press, London, 1991).

For weathering, I use graphite (pencil lead on sandpaper, applied with a dry brush). Upper surfaces would tend to show rust, especially around well-used parts such as hatchways, torpedo-loading hatches, ladders, hand rails, etc. I also find than running your fingers through your hair will pick up natural oils which can then be rubbed on the model. This really works well in taking the flatness out of matt paints, and gives a nice used look, especially on hulls. I may have to resort to using my wife's cats as my hair disappears the older I get.

Hope this helps.

Don