need to delete system file but can't :(

I need to follow these instructions -

Originally Posted by Robbie Hood
i will upload a revert back too mtp mod once the party is over.
If you really need it now then do this :

go to /system/build.prop and open it with a rooted text editor ( most file explorers have one) and remove this line:

Code:
persist.sys.usb.config=mass_storage,adb
then go to /system/etc/init.d and remove the S98MassStorage script.
Reboot and it should work fine.
If not , then you need to check rom customizer/. manage system apps / uninstalled tab and install anything kies, usb or mtp related

I have done the first part and removed - persist.sys.usb.config=mass_storage,adb but I can't change/delete/edit/move the S98MassStorage script, I have tried Root Browser Lite, ZArchiver and ES File Explorer.

Can somebody help me please, recommend a method/app?