I like to use the advice in these 2 leaflets. Around page 17 of of the second one. They are quite big documents, so you may have to be patient while they download:
http://www.wbka.com/wp-content/uploads/2015/04/wbka-booklet-english-PDF.pdf
http://www.wbka.com/wp-content/uploads/2015/02/Swarm-Control-Wally-Shaw.pdf
Giving them brood space is not very effective for swarm control. You would be better off making a split. 