From IMAGINiT Technologies Support Blog:
We can add a modifier to the export dialog box for the items we want to adjust, make sure that you also do this to the sub-categories of the element also, and select the Phase Created modifier and add it to the list, in the separator space, add the separator type you want to use…this will give us
something similar to the following in the cad file:  A-DOOR-Existing

Read more at:
Revit Export: How to Export Phases to the Correct Layer – IMAGINiT Technologies Support Blog

“Free of charge you can try IMAGINiT Utilities for Revit Lite which includes four popular utilities:

Room Renumber, Change Case, Space Update and GridSelect.”

Register / download link

Room Renumber Easily renumber existing rooms into an order defined by selection. Insert rooms into an existing series with the subsequent room numbers “shifted” to make space for the inserted one.

Change Case Instantly match your organization’s or client’s standards on naming with UPPER CASE, Title Case, or lower case. This tool scans your model and automatically fixes “case issues” to whatever standard you specify.

Space Update Seamlessly transfers room names and numbers from the linked Revit Architecture model to the Revit MEP model. Eliminate tedious manual input of room names and numbers in different places.

GridSelect Select Revit elements based on the grid they are on. Select walls, columns, beams and more. Choose the current level or all levels and select collinear or touching beams.

For more info, head over to http://imaginit.com/software-solutions/building-architecture/imaginit-utilities-for-revit