I have previously not had much success with putting virgins into colonies. However this year I brought home 4 that I 'pulled' from a colony I had been asked to help out with. One was caged for 24 hours and released onto the top bars. One was dunked in syrup and dropped into wet bees in an upside down mini-nuc and turned over. The others were let out straight into nucs with a bit of smoke. (Very few older bees in the colonies and apart from the mini-nuc, had been waiting for a queen so definitely queenless. All queens came good.