map - <C-W>-
map = <C-W>+
When you have multiple windows open you can change their size with "Control-w" and '+' or '-' (note that you need to be holding SHIFT to get a '+' sign). This will change the window size one line at a time. If your extremely suave and can count line numbers in your head you can prepend the number of lines you would like to move and the keyboard shortcut isn't all that bad.
I can't count the lines in my head, so I use the above macro. Since I work with multiple windows constantly I have the increase and decrease size bound to '-' and '=', I use equal so that I don't have to press SHIFT for one but not the other.