The rules of procedure herein prescribed shall govern all probate proceedings brought after they take effect and also all further procedure in probate proceedings then pending, except to the extent that in the opinion of the court their application in a particular proceeding when they take effect would not be feasible or would work injustice, in which event the former procedure applies. This act shall take effect and be in force on and after July 1, 1939, and after its publication in the statute book.