Thanks to all of you. This was very useful information. I have done the same on the western line (deboarding at BVI and travelling upto Malad in a local with an express ticket to BDTS) but was not certain on the central line.
I was skeptical on getting down at Dadar and board a local to Ghatkopar as I assume there would be a greater rush in locals from CSTM to TNA when compare to the reverse journey.