If you need something specific, like a perfect projection for lightmap UVs, Blender is really not useful for that. But if you’re just putting textures on a character and the exact dimensions and projection doesn’t matter, marking seams is actually better than planar projections. Perhaps there is a way to apply scaling to selected UVs, but I still have no clue how to use Blender for something like this.
EDIT: just as I am typing this, I am having difficulty UV mapping a plane. facepalm