If I use a plastic fitting to connect to metal, I like to use a plastic MA threaded into the FA metal fitting. If you have a plastic glue joint with metal on the other end, then all the better.
Using a female plastic fitting over a metal pipe is risky.
Whether you use Teflon tape or Teflon based pipe dope is not something to worry about.
Tapered threads are pretty much the only place that a plumber will use Teflon tape or pipe dope.
Galvanized threads are tapered, as are the MA and FA fittings.
Most other connections in plumbing are by rubber seals, compression, slip joints or flares.
: I replaced galvanized 1/2" pipe with cpvc when I relocated a shower in my bathroom. All of cpvc connections are fine however, the connection that I made from the galvanized 3-way fitting to the cpvc is leaking. I used a male brass-to-cpvc connector and 3 revolutions of teflon tape. Should I have used some other type of sealant or pipe dope or could I have possibly over tightened? Any suggestions would be appreciated.