Question about techniques for Texturing.

I’m not very good with texturing, but I’ve always wondered about a few things.

For example, texturing along UV seams, or making straight lines on unstraight UV unwraps. What is the best way to achive that?

For example, you are texturing a hull of a spaceship. You have lines going across certain parts of the ship which follow its curvature and always have the same thickness. Do you use a line tool, or a special kind of brush or is it just practice? I mean, the UV unwrap of a spaceship is not always perfactly square in the area where you need to draw some straight lines.
Or do you use a bezier curve for things like that?

Similarily, what about seams in UV unwraps. The seam of a UVmap is not always a perfectly straight line. What are your techniques for following a seam and having it textured.
Think about the seam on the side of pantleg of a pair of jeans for example. That would be a logical place for a UV seam, since its also the place of the actual seam of the UVmap.

Also, how do you go about making photographic textures follow a certain path.
For certain things, e.g. skin, leather, fabric, etc. It helps to use a photographic texture as a base. But more often than not, the photo doesn’t match your UV unwrap, specifically the tiny structures of fabric or the small wrinkles of skin or leather, don’t necessarily follow your UV unwrap conveniently.
Is there a good way to “bend” certain parts of a photo texture?

check some of these out

http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/UV_Map_Basics

this one deals with organic shapes and uses susan to demopnstrate the technique
http://wiki.blender.org/index.php/Doc:Books/Essential_Blender/10.1.UV_Unwrapping_and_Painting:_Hands_on

there is no line tool, as of yet, ( i suggested it to the devs already ) but check out multiple UV layers, which allow you to have multiple unwraps, which you can clone back and forth between. If you really need a straight line, you can load a grayscale image texture with lines onto your brush, paint it on using projection painting, then use that layer as a mask. ( see latest release notes )