It depends on the relation of the two Views.
A. View2 is Embedded View within View1, OR View2 is a Popup opened by View1:
Pass the property value as a param to the Embedded View/Popup.
B. View2 is on a different Perspective Page than View1:
Bidirectionally bind the custom property on View1 to a custom session property. Bind the custom property on View2 to the same custom session property.
C. View2 is a Docked View of the Perspective Page which contains View1:
You could still use the session property route, or you could use system.perspective.sendMessage() docs as part of a change script on the custom property to broadcast value updates. This would also require a Message Handler be put in place on View2 to listen for the broadcasts.
If you provide a better idea of how the Views will be used, I might be able to help a bit more.