Most molding is 1 of 2 ways attached by the plastic push style snaps or by heavy duty double sided tape.
If you and the client wants it off, heavy duty fishing line used in a saw type motion does good if its the double sided tape if its the push in snap style there is body tools that help with them.
Theres also this stuff that holds molding,
METAL BONDING PANEL ADHESIVE:
3M - Two-part epoxy used to bond steel, aluminum, SMC, and FRP (traditional fiberglass). The primary use is to replace auto body quarter panels, roofs, box sides, van sides, utility vehicle sides and door skins. OEM Approved.
DURAMIX: Tenacious bonding auto body doorskin adhesive that can also be used to bond steel parts when a 45 minute work time is desired. Bonds doorskins is 2 hours. Other panels and parts are bonded in 6 hours (use heat to reduce declamp time to 1 1/2 hours.
Heres a site that shows some of the snaps and fasterners used on panels,
http://www.wclco.com/Plastic_Components/Plastic_Fasteners.php
Hope that helps.