Never PTFE on any compression joint, before, after or over the olive!
Thin smear of jointing compound on the fitting side of the pipe and that's that.
Old fittings should have the olive replaced and remade. If this becomes impossible then paste will still do the trick.
If, as mentioned above, the pipe doesn't enter quite straight or is under undue pressure then the pipework should be altered accordingly.
Trade point of view not DIY.
Completely agree, a smear of Boss White(generic name) on the fitting side of all compression olives.
If you ever go to a job & see PTFE on compression fitting, disconnect at your pearl!! It's been done by a DaftyDIYer or cowboy!! It'll blown off in your hands!!
Regardless of the type of olive, copper or brass always just use Boss White joint paste.