The quickest way to swap buffers between windows. Based on switch-window package.
(require 'swap-buffers)
Bind your favorite key to 'swap-buffers:
(global-set-key (kbd "C-c b") 'swap-buffers)
By default swap-buffers move focus to second window.
Press C-u C-c b to keep focus in first window
Before
Choose window for swap
After
swap-buffers-dired-find-file works like dired-find-file-other-window, but allow to specify concrete window.