Practice of the other three Brahmaviharas

Metta has received plenty of attention and focus of practice. Even a search of Buddhism SE shows over 170 posts with the word "metta" in it. Comparatively, the other three Brahmaviharas are not so often discussed or focused in similar depth. How do we practise them? What are the benefits that can be gained out of the practice? Canonical quotes appreciated. Theravada preferable, but answers from the perspective of other traditions are also welcomed.