Ketzos Hachoshen 362:1 - Kinyan yeiush veShinui Rshus
Whether a gazlan who gifts or sells the gezeila to a third party is a da'as acherres makneh. (Can he therefore, gift it to a child?)
In this shiur, the Ketzos brilliantly clarifies two schools of thought in the meachanism of shinui reshus: On the one hand Tosfos, the Rosh and the Ramban (in Milchamos) and on the other hand the Rambam and the Rashbah. He shows how according to the first school Yeiush is the kinyan and shinui reshus creates the condition of heteira for yeiush to operate in the same way as it does for a motzei aveidah. The second school considers shunui reshus as the kinyan and yeiush is an additional requirement for the kinyan to operate. According to the second school, the act of shinui reshus even gives the makneh (in this case the gazlan) the rights of a da'as acherres makneh.