how did yoruichi help urahara escape from the soul society

with sangetsu

From what I remember, she had Kisuke wear that ছদ্মবেশ that keeps his reiatsu from being felt, and then they গাউন away with the Visoreds, probably cutting through one of the undiscovered Senkaimon... At least, that's how I think it went. It's been a while, since I watched Bleach, though.