I dunno if this will help you or not. “Cast to” node is Type Conversion. A programming term: http://en.wikipedia.org/wiki/Type_conversion
Like, if I want to get my current player, I would use “cast to” to my current player class. So in UE it’s something like this:
Get Player Pawn -> Cast to “MyCustomCharacterBP” -> Set Property.
In your case, you’re already getting the custom class you need right from the “Get all actors of class”. So you’re done. No cast needed. In the above we’re getting a reference to our player pawn. So you have to convert its type to your custom subclass (should be a child of the type, “Get Player Pawn” returns Pawn class so your custom subclass must be a child of Pawn…)